New Journal of Physics - Diebold, Tulane - Tulane University

New Journal of Physics - Diebold, Tulane - Tulane University

New Journal of Physics

The open-access journal for physics

Best of 2008



The normalized second-order correlation function of an initially spatially coherent Gaussian

profile beam that has passed through a water/glycerol mixture containing polystyrene

microspheres, taken from the article ‘Modelling of classical ghost images obtained using

scattered light’ by S Crosby, S Castelletto, C Aruldoss, R E Scholten and A Roberts 2007 New

Journal of Physics 9 285

Visualization of a current roll in a simulation of magnetohydrodynamic turbulence showing the

current intensity and integrated velocity field lines, taken from the article ‘Flow visualization and

field line advection in computational fluid dynamics: application to magnetic fields and

turbulent flows’ by Pablo Mininni, Ed Lee, Alan Norton and John Clyne 2008 New Journal of

Physics 10 125007

Magnified view of the field pattern within a 3D barium strontium titanate electromagnetic cloak,

taken from the article ‘Transformation optics for the full dielectric electromagnetic cloak and

metal–dielectric planar hyperlens’ by D P Gaillot, C Croënne, F Zhang and D Lippens 2008

New Journal of Physics 10 115039

A detector XY view of a 4-jet e + e - collision event, taken from the article ‘Innovations in ILC

detector design using a particle flow algorithm approach’ by Stephen R Magill 2007 New

Journal of Physics 9 409

Nesting of the 2H-TaSe 2 Fermi surface showing the real part of the Lindhard function at �✇0 as

a function of momentum, taken from the article ‘Fermi surface nesting in several transition

metal dichalcogenides’ by D S Inosov, V B Zabolotnyy, D V Evtushinsky, A A Kordyuk, B

Büchner, R Follath, H Berger and S V Borisenko 2008 New Journal of Physics 10 125027

A fluorescence image of a commercially stained cabbage flower bud cross-section, taken from

the article ‘Dynamic contrast enhancement in widefield microscopy using projector-generated

illumination patterns’ by Edward Carlo Samson and Carlo Mar Blanca 2007 New Journal of

Physics 9 363

A colour-coded visualization of the Minkowski functional for a bone microstructure, taken from

the article ‘Strength through structure: visualization and local assessment of the trabecular

bone structure’ by C Räth, R Monetti, J Bauer, I Sidorenko, D Müller, M Matsuura,

E-M Lochmüller, P Zysset and F Eckstein 2008 New Journal of Physics 10 125010

A snapshot from an animation illustrating the merger of the Milky Way and Andromeda galaxies,

taken from the article ‘Visualizing astrophysical N-body systems’ by John Dubinski 2008 New

Journal of Physics 10 125002

Visualization of a type 1a supernova at the onset of the detonation phase, taken from the article

‘Thermonuclear supernovae: a multi-scale astrophysical problem challenging numerical

simulations and visualization’ by F K Röpke and R Bruckschen 2008 New Journal of Physics

10 125009

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2004 2005 2006 2007 2008

Subject distribution

Atomic and molecular physics 11%

Biophysics 4%

Condensed matter 33%

Cosmology and astrophysics 1%

Nuclear and particle physics 4%

Optics 11%

Plasmas 4%

Quantum physics 8%

Soft matter 3%

Statistical physics 7%

Surface science 14%


Dear colleague,

New Journal of Physics: Best of 2008

Last year saw New Journal of Physics (NJP) celebrate its 10th anniversary as an openaccess

journal serving the whole of physics. As it moves into a new decade, I am

delighted to present here, on behalf of the Editorial Board and NJP staff team, a selection

of abstracts showcasing just some of the journal’s article highlights from 2008. Identified

on the basis of criteria that included referee endorsements, readership and citation

levels, and simple broad appeal, I hope that this compilation provides a real flavour of

the diversity, breadth and quality of NJP’s content last year.

Passing the 10 year mark was just one milestone achieved by NJP in 2008. With a

readership now extending to over 190 countries and more than 50000 downloads each

month, the total of number of downloads now exceeds 2.5 million underlining NJP’s

ongoing success in achieving the widest possible dissemination of its content by

removing financial barriers to readers worldwide.

Attracted by the enhanced reputation, high visibility and fast publication that the journal

stands for, authors across the world are also increasingly choosing NJP and last year we

published our 2000th article. Between 2007 and 2008 the journal grew by 50% and

aided by a diverse programme of invited focus issues, NJP is serving communities right

across physics by publishing in the most active and dynamic areas. I am also happy to

report that NJP’s modest publication charges are stable and now fully sustain the journal.

Now firmly placed not only at the forefront of the open-access movement, but also as a

leading physics journal in its own right, NJP’s success is due only to the fantastic support

of the physics community worldwide. On behalf of the Institute of Physics and Deutsche

Physikalische Gesellschaft, I would therefore like to thank all of our authors, referees,

partners, supporters and, last but not least, our Board members for their vital

contribution to NJP.

And finally, thank you for your support! I hope that you will consider NJP as a first-choice

publication outlet for your next paper.

Professor Eberhard Bodenschatz

Editor-in-Chief, New Journal of Physics


New Journal of Physics 3

New Journal of Physics: Best of 2008



The resource theory of quantum reference frames: manipulations and monotones 8

Gilad Gour and Robert W Spekkens

Experimental verification of the feasibility of a quantum channel between space and Earth 8

P Villoresi, T Jennewein, F Tamburini, M Aspelmeyer, C Bonato, R Ursin, C Pernechele, V Luceri, G Bianco, A Zeilinger and C Barbieri

A convergent hierarchy of semidefinite programs characterizing the set of quantum correlations 8

Miguel Navascués, Stefano Pironio and Antonio Acín

Squeezing the limit: quantum benchmarks for the teleportation and storage of squeezed states 9

M Owari, M B Plenio, E S Polzik, A Serafini and M M Wolf

Illustration of quantum complementarity using single photons interfering on a grating 9

V Jacques, N D Lai, A Dréau, D Zheng, D Chauvat, F Treussart, P Grangier, and J-F Roch


The adiabatic instability on cosmology’s dark side 10

Rachel Bean, Éanna É Flanagan and Mark Trodden

Observation of negative-frequency waves in a water tank: a classical analogue to the Hawking effect? 10

Germain Rousseaux, Christian Mathis, Philippe Maïssa, Thomas G Philbin and Ulf Leonhardt

Area–angle variables for general relativity 10

Bianca Dittrich and Simone Speziale

Thermonuclear supernovae: a multi-scale astrophysical problem challenging numerical simulations and visualization 11

F K Röpke and R Bruckschen


4 New Journal of Physics



Study of photo-proton reactions driven by bremsstrahlung radiation of high-intensity laser generated electrons 11

K M Spohr, M Shaw, W Galster, K W D Ledingham, L Robson, J M Yang, P McKenna, T McCanny, J J Melone, K-U Amthor,

F Ewald, B Liesfeld, H Schwoerer and R Sauerbrey

Discrimination of nuclear recoils from alpha particles with superheated liquids 12

F Aubin, M Auger, M-H Genest, G Giroux, R Gornea, R Faust, C Leroy, L Lessard, J-P Martin, T Morlat, M-C Piro, N Starinski,

V Zacek, B Beltran, C B Krauss, E Behnke, I Levine, T Shepherd, P Nadeau, U Wichoski, S Pospisil, I Stekl, J Sodomka, K Clark,

X Dai, A Davour, C Levy, A J Noble and C Storey

Heavy ion microprobes: a unique tool for bystander research and other radiobiological applications 12

K O Voss, C Fournier and G Taucher-Scholz

Experimental studies of compensation of beam–beam effects with Tevatron electron lenses 13

V Shiltsev, Y Alexahin, K Bishofberger, V Kamerdzhiev, V Parkhomchuk, V Reva, N Solyak, D Wildman, X-L Zhang

and F Zimmermann

New Journal of Physics: Best of 2008


The trapped two-dimensional Bose gas: from Bose–Einstein condensation to Berezinskii–Kosterlitz–Thouless physics 13

Z Hadzibabic, P Krüger, M Cheneau, S P Rath and J Dalibard

Elastic electron scattering from 3-hydroxytetrahydrofuran: experimental and theoretical studies 14

V Vizcaino, J Roberts, J P Sullivan, M J Brunger, S J Buckman, C Winstead and V McKoy

Spin squeezing in optical lattice clocks via lattice-based QND measurements 14

D Meiser, Jun Ye and M J Holland

Theory of cavity-assisted microwave cooling of polar molecules 14

Margareta Wallquist, Peter Rabl, Mikhail D Lukin and Peter Zoller


Diffractive hygrochromic effect in the cuticle of the hercules beetle Dynastes hercules 15

M Rassart, J-F Colomer, T Tabarrant and J P Vigneron

Annihilation assisted upconversion: all-organic, flexible and transparent multicolour display 15

Tzenka Miteva, Vladimir Yakutkin, Gabriele Nelles and Stanislav Baluschev

Transmutation of singularities in optical instruments 15

Tomás˘ Tyc and Ulf Leonhardt

Transformation optics: approaching broadband electromagnetic cloaking 16

A V Kildishev, W Cai, U K Chettiar and V M Shalaev

Vector frequency-comb Fourier-transform spectroscopy for characterizing metamaterials 16

T Ganz, M Brehm, H G von Ribbeck, D W van der Weide and F Keilmann


Electron wavepacket control with elliptically polarized laser light in high harmonic generation from aligned molecules 16

Y Mairesse, N Dudovich, J Levesque, M Yu Ivanov, P B Corkum and D M Villeneuve

Subtracting photons from arbitrary light fields: experimental test of coherent state invariance 17

by single-photon annihilation

A Zavatta, V Parigi, M S Kim, and M Bellini

Conditional preparation of single photons using parametric downconversion: a recipe for purity 17

P J Mosley, J S Lundeen, B J Smith and I A Walmsley

Imaging of carrier-envelope phase effects in above-threshold ionization with intense few-cycle laser fields 18

M F Kling, J Rauschenberger, A J Verhoef, E Hasovic, T Uphues, D B Milos˘evic, H G Muller and M J J Vrakking

` `


New Journal of Physics 5

New Journal of Physics: Best of 2008



Structure of epitaxial graphene on Ir(111) 20

Alpha T N’Diaye, Johann Coraux, Tim N Plasa, Carsten Busse and Thomas Michely

XMCD studies on Co and Li doped ZnO magnetic semiconductors 20

Thomas Tietze, Milan Gacic, Gisela Schütz, Gerhard Jakob, Sebastian Brück and Eberhard Goering

Pressure effect on superconducting properties of LaO 1-x F x FeAs (x = 0.11) superconductor 20

W Lu, J Yang, X L Dong, Z A Ren, G C Che and Z X Zhao

A new crystalline phase of four-fold coordinated silicon and germanium 21

Yoshitaka Fujimoto, Takashi Koretsune, Susumu Saito, Takashi Miyake and Atsushi Oshiyama

Onset of magnetic order in strongly-correlated systems from ab initio electronic structure calculations: 21

application to transition metal oxides

I D Hughes, M Däne, A Ernst, W Hergert, M Lüders, J B Staunton, Z Szotek and W M Temmerman


6 New Journal of Physics

Intense single attosecond pulses from surface harmonics using the polarization gating technique 18

S G Rykovanov, M Geissler, J Meyer-ter-Vehn and G D Tsakiris

Feasibility of electrostatic microparticle propulsion 18

Th Trottenberg, H Kersten and H Neumann

Complex plasma laboratory PK-3 Plus on the International Space Station 19

H M Thomas, G E Morfill, V E Fortov, A V Ivlev, V I Molotkov, A M Lipaev, T Hagl, H Rothermel, S A Khrapak, R K Suetterlin,

M Rubin-Zuzic, O F Petrov, V I Tokarev and S K Krikalev

Space and time resolved measurements of the heating of solids to ten million kelvin by a petawatt laser 19

M Nakatsutsumi, J R Davies, R Kodama, J S Green, K L Lancaster, K U Akli, F N Beg, S N Chen, D Clark, R R Freeman, C D Gregory,

H Habara, R Heathcote, D S Hey, K Highbarger, P Jaanimagi, M H Key, K Krushelnick, T Ma, A MacPhee, A J MacKinnon,

H Nakamura, R B Stephens, M Storm, M Tampo, W Theobald, L Van Woerkom, R L Weber, M S Wei, N C Woolsey and P A Norreys

Single atoms on an optical nanofibre 22

K P Nayak and K Hakuta

Nanoscale superconducting properties of amorphous W-based deposits grown with a focused-ion-beam 22

I Guillamón, H Suderow, S Vieira, A Fernández-Pacheco, J Sesé, R Córdoba, J M De Teresa and M R Ibarra

Nanoelectromechanics of suspended carbon nanotubes 22

A K Hüttel, M Poot, B Witkamp and H S J van der Zant

Nanoplasmonic renormalization and enhancement of Coulomb interactions 22

M Durach, A Rusina, V I Klimov and M I Stockman

New Journal of Physics: Best of 2008


The shortcomings of semi-local and hybrid functionals: what we can learn from surface science studies 23

A Stroppa and G Kresse

Modulation of surface plasmon coupling-in by one-dimensional surface corrugation 23

F López-Tejeira, Sergio G Rodrigo, L Martín-Moreno, F J García-Vidal, E Devaux, J Dintinger, T W Ebbesen, J R Krenn, I P Radko,

S I Bozhevolnyi, M U González, J C Weeber and A Dereux

On the internal energy of sputtered clusters 24

A Wucher, C Staudt, S Neukermans, E Janssens, F Vanhoutte, E Vandeweert, R E Silverans and P Lievens

Surface structure of Sn-doped In 2 O 3 (111) thin films by STM 24

Erie H. Morales, Yunbin He, Mykola Vinnichenko, Bernard Delley, and Ulrike Diebold


Self-organization and the selection of pinwheel density in visual cortical development 24

Matthias Kaschube, Michael Schnabel and Fred Wolf

Emergence of agent swarm migration and vortex formation through inelastic collisions 25

D Grossman, I S Aranson and E Ben Jacob

Visualization of spiral and scroll waves in simulated and experimental cardiac tissue 25

E M Cherry and F H Fenton

The stochastic dance of circling sperm cells: sperm chemotaxis in the plane 26

B M Friedrich and F Jülicher


Complex network analysis of state spaces for random Boolean networks 26

Amer Shreim, Andrew Berdahl, Vishal Sood, Peter Grassberger and Maya Paczuski

Traffic jams without bottlenecks—experimental evidence for the physical mechanism of the formation of a jam 27

Yuki Sugiyama, Minoru Fukui, Macoto Kikuchi, Katsuya Hasebe, Akihiro Nakayama, Katsuhiro Nishinari, Shin-ichi Tadaki and

Satoshi Yukawa

Specialization and herding behavior of trading firms in a financial market 27

Fabrizio Lillo, Esteban Moro, Gabriella Vaglica and Rosario N Mantegna

Third quantization: a general method to solve master equations for quadratic open Fermi systems 28

Tomaz˘ Prosen

Heat conduction and Fourier’s law in a class of many particle dispersing billiards 28

Pierre Gaspard and Thomas Gilbert


Editorial Board and Journal Team 29

New Journal of Physics 7

New Journal of Physics: Best of 2008


Experimental verification

of the feasibility of a

quantum channel between

space and Earth

P Villoresi 1 , T Jennewein 2 , F Tamburini 3 , M Aspelmeyer 2,4 , C Bonato 1 ,

R Ursin 4 , C Pernechele 5 , V Luceri 6 , G Bianco 7 , A Zeilinger 2,4 and C Barbieri 3

1 Department of Information Engineering, University of Padova and INFM-CNR

LUXOR Laboratory for Ultraviolet and X-ray Optical Research, Padova, Italy

2 Institute for Quantum Optics and Quantum Information (IQOQI), Austrian

Academy of Sciences, Vienna, Austria

3 Department of Astronomy, University of Padova, Italy

4 Faculty of Physics, Institute for Experimental Physics, University of Vienna, Austria

5 INAF-Cagliari, Capoterra (CA), Italy

6 Centro di Geodesia Spaziale ‘G Colombo', e-GEOS SpA, Matera, Italy

7 Centro di Geodesia Spaziale ‘G Colombo', Agenzia Spaziale Italiana, Matera, Italy

Extending quantum communication to space environments would enable

us to perform fundamental experiments on quantum physics as well as

applications of quantum information at planetary and interplanetary scales.

Here, we report on the first experimental study of the conditions for the

implementation of the single-photon exchange between a satellite and an

Earth-based station. We built an experiment that mimics a single photon

source on a satellite, exploiting the telescope at the Matera Laser Ranging

Observatory of the Italian Space Agency to detect the transmitted photons.

Weak laser pulses, emitted by the ground-based station, are directed

toward a satellite equipped with cube-corner retroreflectors. These reflect a

small portion of the pulse, with an average of less-than-one photon per

pulse directed to our receiver, as required for faint-pulse quantum

communication. We were able to detect returns from satellite Ajisai, a low-

Earth orbit geodetic satellite, whose orbit has a perigee height of 1485 km.

P Villoresi et al 2008 New J. Phys. 10 033038

The experimental set-up installed at the MLRO: a train of pulses of 700-ps duration, 532 nm

wavelength, 490 nJ of energy and 17 kHz repetition rate is sent toward the satellite via the MLRO

telescope, whose primary mirror has 1.5 m aperture. A fraction of the photons in the downlink

path are collected by the telescope and detected by a gated silicon avalanche photo diode

detector (D), placed behind a spectral filter (F). The separation in polarization of the uplink and

downlink paths is accomplished by a polarizing beam-splitter (PBS) and a QWP.

8 New Journal of Physics

The resource theory of

quantum reference frames:

manipulations and


Gilad Gour 1 and Robert W Spekkens 2

1 Institute for Quantum Information Science and Department of Mathematics and

Statistics, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4,


2 Department of Applied Mathematics and Theoretical Physics, University of

Cambridge, Cambridge CB3 0WA, UK

Quantum information processing rests on our ability to manipulate the

state of a quantum system in a controlled way. However, quantum systems

do not exist independent of their environment. Uncontrollable interactions

with the environment might lead to dissipation and the irreversible loss of

information. An important step towards the practical realisation of quantum

computing was therefore the identification of a large set of states, which

do not couple to the environment. These became known as decoherencefree


In this paper we give a detailed description of the decoherence-free states

of a system consisting of N atoms trapped inside an optical cavity.

Moreover, we proposed how to manipulate these states very efficiently with

the help of weak laser pulses. Normally, local interactions like these cannot

create entanglement between atomic qubits. However, we could show that

the presence of relatively large spontaneous decay rates renders the

behaviour of the system dramatically. It suppresses the population of non

decoherence-free states so that the laser driving transfers the system in

general into an entangled state. This shows that one can actually use

dissipation to perform quantum computational tasks.

Since the publication of our manuscript, many quantum computing

schemes have been proposed in which dissipation and measurements are

an integral part in generating and

manipulating stable qubits. Our

work mainly focuses on the design

of simpler, more robust and

scalable quantum computing

architectures based on the use of


measurements, which are readily


A Venn diagram of frameness monotones for

pure states.

Gilad Gour et al 2008 New J. Phys. 10


A convergent hierarchy of

semidefinite programs

characterizing the set of

quantum correlations

Miguel Navascués1,2 , Stefano Pironio2 and Antonio Acín2,3 1 Institute for Mathematical Sciences, Imperial College London, SW7 2PG, UK

2 ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels (Barcelona), Spain

3 ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona,


We are interested in the problem of characterizing the correlations that arise

when performing local measurements on separate quantum systems. In a

previous work (Navascués et al 2007 Phys. Rev. Lett. 98 010401), we

introduced an infinite hierarchy of conditions necessarily satisfied by any

set of quantum correlations. Each of these conditions could be tested using

semidefinite programming. We present here new results concerning this

hierarchy. We prove in particular that it is complete, in the sense that any

set of correlations satisfying every condition in the hierarchy has a quantum

representation in terms of commuting measurements. Although our tests

are conceived to rule out non-quantum correlations, and can in principle

certify that a set of correlations is quantum only in the asymptotic limit

where all tests are satisfied, we show that in some cases it is possible to

conclude that a given set of correlations is quantum after performing only a

finite number of tests. We provide a criterion to detect when such a situation

arises, and we explain how to reconstruct the quantum states and

measurement operators reproducing the given correlations. Finally, we

present several applications of our approach. We use it in particular to

bound the quantum violation of various Bell inequalities.

Miguel Navascués et al 2008 New J. Phys. 10 073013

Local measurements on a system shared by two observers viewed as a black-box process.

Alice chooses a measurement input X and obtains a measurement output a � X. Similarly, Bob

chooses an input Y and receives an output b � Y . The behavior of the system is characterized

by the joint probabilities P(a, b).

Squeezing the limit:

quantum benchmarks for

the teleportation and

storage of squeezed states

M Owari1,2, M B Plenio1,2, E S Polzik3, A Serafini4 and M M Wolf3 1 Institute for Mathematical Sciences, 53 Prince’s Gate, Imperial College London,

London SW7 2PG, UK

2 QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, UK

3 Niels Bohr Institute, Copenhagen University, Blegdamsvej 17, DK-2100

Copenhagen Ø, Denmark

4 Department of Physics and Astronomy, University College London, Gower Street,

London WC1E 6BT, UK

We derive fidelity benchmarks for the quantum storage and teleportation of

squeezed states of continuous variable systems, for input ensembles where

the degree of squeezing s is fixed, no information about its orientation in

phase space is given, and the distribution of phase-space displacements is

a Gaussian. In the limit where the latter becomes flat, we prove analytically

that the maximal classical achievable fidelity (which is 1/2 without

squeezing, for s = 1) is given by √s/(1+s), vanishing when the degree of

squeezing diverges. For mixed states, as well as for general distributions of

displacements, we reduce the determination of the benchmarks to the

solution of a finite-dimensional semidefinite program, which yields

accurate, certifiable bounds thanks to a rigorous analysis of the truncation

error. This approach may be easily adapted to more general ensembles of

input states.

M Owari et al 2008 New J. Phys. 10 113014

New Journal of Physics: Best of 2008

Fidelity benchmarks F(s,�) for measure-and-prepare schemes on ensembles with squeezing s,

flatly distributed displacements and random phase-space orientations, as a function of the

squeezing s (before additive noise is applied). The continuous (red) curve refers to pure states

(� = 0), whereas the dashed (blue) and dotted (green) curves refer to mixed states, for � = 0.5

and � = 1, respectively.

Illustration of quantum

complementarity using

single photons interfering

on a grating

V Jacques1 , N D Lai1 , A Dréau1 , D Zheng1 , D Chauvat1 , F Treussart1 ,

P Grangier2 , and J-F Roch1 1 Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure

de Cachan, UMR CNRS 8537, Cachan, France

2 Laboratoire Charles Fabry de l’Institut d’Optique, UMR CNRS 8501, Palaiseau,


A recent experiment performed by S S Afshar et al has been interpreted as a

violation of Bohr’s complementarity principle between interference visibility

and which-path information in a two-path interferometer. We have

reproduced this experiment, using true single-photon pulses propagating in

a two-path wavefrontsplitting interferometer realized with a Fresnel’s

biprism, and followed by a grating with adjustable transmitting slits. The

measured values of interference visibility V and which-path information,

characterized by the distinguishability parameter D, are found to obey the

complementarity relation V 2 + D 2 ≤ 1. This result demonstrates that the

experiment can be perfectly explained by the Copenhagen interpretation of

quantum mechanics.

V Jaques et al 2008 New J. Phys. 10 123009

Experimental realization of the modified Afshar’s experiment based on a Fresnel’s biprism and

single-photon pulses emitted by an individual NV colour centre in a diamond nanocrystal, excited

in the pulsed regime at a 4-MHz repetition rate.

New Journal of Physics 9

New Journal of Physics: Best of 2008


The adiabatic instability on

cosmology’s dark side

Rachel Bean1 , Éanna É Flanagan2 and Mark Trodden3 1 Department of Astronomy, Cornell University, Ithaca, NY 14853, USA

2 Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853,


3 Department of Physics, Syracuse University, Syracuse, NY 13244, USA

We consider theories with a nontrivial coupling between the matter and

dark energy sectors. We describe a small scale instability that can occur in

such models when the coupling is strong compared to gravity, generalizing

and correcting earlier treatments. The instability is characterized by a

negative sound speed squared of an effective coupled dark matter/dark

energy fluid. Our results are general, and applicable to a wide class of

coupled models and provide a powerful, redshift-dependent tool,

complementary to other constraints, with which to rule many of them out.

A detailed analysis and applications to a range of models are presented

in a longer companion paper.

Rachel Bean et al 2008 New J. Phys. 10 033006

Bottom panel: the two component coupled dark energy (CDE) model, with λ = 2 and coupling

C = –20 with H 0 =70kms –1 Mpc –1 , Ω b = 0.05, Ω c = 0.2, Ω co = 0.05, and Ω V = 0.70.

Top panel: the growth of the fractional over-density δ = δρ/ρ for k = 0.01 Mpc –1 for the coupled

CDM component, δ co , (red long dashed line) and uncoupled component, δ c , (black full line) in

comparison to the growth for the ΛCDM model (black dashed line). At late times the adiabatic

behavior triggers a dramatic increase in the rate of growth of both uncoupled and coupled

components, leading to structure predictions inconsistent with observations.

Observation of negativefrequency

waves in a water

tank: a classical analogue

to the Hawking effect?

10 New Journal of Physics

Germain Rousseaux1,2 , Christian Mathis2 , Philippe Maïssa2 ,

Thomas G Philbin3,4 and Ulf Leonhardt3 1 ACRI, Laboratoire Génimar, 260 route du Pin Montard, BP 234, 06904 Sophia-

Antipolis Cedex, France

2 Université de Nice-Sophia Antipolis, Laboratoire J-A Dieudonné, UMR CNRS-UNSA

6621, Parc Valrose, 06108 Nice Cedex 02, France

3 School of Physics and Astronomy, University of St Andrews, North Haugh, St

Andrews KY16 9SS, Scotland, UK

4 Max Planck Research Group of Optics, Information and Photonics, Günther-

Scharowsky-Strasse 1, Bau 24, D-91058 Erlangen, Germany

The conversion of positive-frequency waves into negative-frequency waves

at the event horizon is the mechanism at the heart of the Hawking radiation

of black holes. In black-hole analogues, horizons are formed for waves

propagating in a medium against the current when and where the flow

exceeds the wave velocity. We report on the first direct observation of

negative-frequency waves converted from positive-frequency waves in a

moving medium. The measured degree of mode conversion is significantly

higher than that expected from the theory.

Germain Rousseaux et al 2008 New J. Phys. 10 053015

Water–wave horizon.

Area–angle variables for

general relativity

Bianca Dittrich and Simone Speziale

Perimeter Institute, 31 Caroline St. N, Waterloo, ON, N2L 2Y5, Canada

We introduce a modified Regge calculus for general relativity on a

triangulated four-dimensional Riemannian manifold where the fundamental

variables are areas and a certain class of angles. These variables satisfy

constraints which are local in the triangulation. We expect the formulation to

have applications to classical discrete gravity and non-perturbative

approaches to quantum gravity.

B Dittrich and S Speziale 2008 New J. Phys. 10 083006

The geometric meaning of equation (2): the 2D angle

� i j,kl belonging to the shaded triangle can be

expressed in terms of 3D angles associated with the

thick edges of the tetrahedron k, or equivalently of

the tetrahedron l.

Thermonuclear supernovae:

a multi-scale astrophysical

problem challenging

numerical simulations

and visualization

F K Röpke1 and R Bruckschen2 1 Max-Planck-Institut für Astrophysics, Karl-Schwarzschild-Strasse 1, D-85741

Garching, Germany

2 Rechenzentrum der Max-Planck-Gesellschaft am Max-Planck-Institut für

Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching, Germany

The numerical modeling of type Ia supernovae is a demanding

astrophysical task. Relevant physical processes take place on vastly

different length- and timescales. This multi-scale character of the object

poses challenges to the numerical approaches. We discuss an

implementation that accounts for these problems by employing a large

eddy simulation (LES) strategy for treating turbulence effects and a level-set

technique to represent the thin thermonuclear flames. It is demonstrated

that this approach works efficiently in simulations of the deflagration model

and the delayed detonation model of type Ia supernovae. The resulting data

reflect the multi-scale nature of the problem. Therefore, visualization has to

be tackled with special techniques. We describe an approach that enables

the interactive exploration of large datasets on commodity hardware. To this

end, out-of-core methods are employed and the rendering of the data is

achieved by a hybrid particle-based and texture-based volume-rendering


F K Röpke and R Bruckschen 2008 New J. Phys. 10 125009

Visualization of the delayed detonation simulation at the onset of the detonation phase: 0.72 s

(top left), 0.80 s (top right), and 0.90 s (bottom) after the ignition of the deflagration flame,

which is shown as a blue isosurface. The detonation front is indicated by the white isosurface and

volume-rendered (yellow/orange) is the density of the exploding WD star.


New Journal of Physics: Best of 2008

Study of photo-proton

reactions driven by

bremsstrahlung radiation of

high-intensity laser

generated electrons

K M Spohr1 , M Shaw1 , W Galster2 , K W D Ledingham2,3,4 , L Robson2,3 ,

J M Yang2,5 , P McKenna2 , T McCanny2 , J J Melone1 , K-U Amthor4 , F Ewald4,6 ,

B Liesfeld4 , H Schwoerer4,7 and R Sauerbrey4,8 1 SUPA, School of Engineering and Science, University of the West of Scotland, High

Street 1, Paisley PA1 2BE, UK

2 SUPA, Department of Physics, University of Strathclyde, Rottenrow, Glasgow

G4 0NG, UK

3 AWE plc, Aldermaston, Reading RG7 4PR, UK

4 Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena,

Max-Wien-Platz 1, 07743 Jena, Germany

5 Present address: Research Center of Laser Fusion, China Academy of Engineering

Physics, PO Box 919-986, 621900 Miangyang, People’s

Republic of China.

6 Present address: Laboratoire d’Optique Appliquée, École Polytechnique, ENSTA,

CNRS, UMR 7639, 91761 Palaiseau, France.

7 Present address: Laser Research Institute, University of Stellenbosch,

Private Bag X1, 7602 Matieland, South Africa.

8 Present address: Forschungszentrum Rossendorf e.V., PO Box 510119, Bautzner

Landstr. 128, 01328 Dresden, Germany.

Photo-nuclear reactions were investigated using a high power table-top

laser. The laser system at the University of Jena (I ∼ 3–5 × 10 19 Wcm –2 )

produced hard bremsstrahlung photons (kT ∼ 2.9 MeV) via a laser–gas

interaction which served to induce (γ, p) and (γ, n) reactions in Mg, Ti, Zn

and Mo isotopes. Several (γ, p) decay channels were identified using

nuclear activation analysis to determine their integral reaction yields. As the

laser-generated bremsstrahlung spectra stretches over the energy regime

dominated by the giant dipole resonance (GDR), these yield measurements

were used in conjunction with theoretical estimates of the resonance

energies E res and their widths Γ res to derive the integral reaction crosssection

σ int (γ,p) for 25 Mn, 48, 49 Ti, 68 Zn and 97, 98 Mo isotopes for the first

time. This study enabled the determination of the previously unknown

� int (γ,n)/� int (γ,p) cross-section ratios for these isotopes. The experiments

were supported by extensive model calculations (Empire) and the results

were compared to the Thomas–Reiche–Kuhn (TRK) dipole sum rule as well

as to the experimental data in neighboring isotopes and good agreement

was observed. The Coulomb barrier and the neutron excess strongly

influence the � int (γ,n)/� int (γ,p) ratios for increasing target proton and

neutron numbers.

K M Spohr et al 2008 New J. Phys. 10 043037

Schematic view of the experimental set-up. The target was placed in direct contact with the

tantalum converter to narrowly confine the activated volume.

New Journal of Physics 11

New Journal of Physics: Best of 2008

Discrimination of nuclear

recoils from alpha particles

with superheated liquids

F Aubin1,7 , M Auger1,8 , M-H Genest1,9 , G Giroux1 , R Gornea1,8 , R Faust1 ,

C Leroy1 , L Lessard1 , J-P Martin1 , T Morlat1,10 , M-C Piro1 , N Starinski1 ,

V Zacek1 , B Beltran2 , C B Krauss2 , E Behnke3 , I Levine3 , T Shepherd3 ,

P Nadeau4 , U Wichoski4 , S Pospisil5 , I Stekl5 , J Sodomka5 , K Clark6,11 ,

X Dai6 , A Davour6 , C Levy6 , A J Noble6 and C Storey6 1 Département de Physique, Université de Montréal, Montréal, H3C 3J7, Canada

2 Department of Physics, University of Alberta, Edmonton, T6G 2G7, Canada

3 Department of Physics and Astronomy, Indiana University South Bend,

South Bend, IN 46634, USA

4 Department of Physics, Laurentian University, Sudbury, P3E 2C6, Canada

5 Institute of Experimental and Applied Physics, Czech Technical University in

Prague, Prague, Cz-12800, Czech Republic

6 Department of Physics, Queens University, Kingston, K7L 3N6, Canada

7 Present address: Department of Physics, McGill University, Montréal, H3A 2T8,


8 Present address: Institut de Physique, Université de Neuchâtel, CH-2000,

Neuchâtel, Switzerland.

9 Present address: Fakultät für Physik, Ludwig-Maximilians-Universität,

D-85748 Garching, Germany.

10 Present address: Centro de Física Nuclear, Universidade de Lisboa,

1649-003, Portugal.

11 Present address: Department of Physics, Case Western Reserve University,

Cleveland OH 44106-7079, USA.

The PICASSO collaboration observed for the first time a significant difference

between the acoustic signals induced by neutrons and alpha particles in a

detector based on superheated liquids. This new discovery offers the

possibility of improved background suppression and could be especially

useful for dark matter experiments. This new effect may be attributed to the

formation of multiple bubbles on alpha tracks, compared to single

nucleations created by neutron-induced recoils.

F Aubin et al 2008 New J. Phys. 10 103017

Amplitude distributions of neutron and alpha particle induced events for two detectors with C 4 F 10

droplets of ~ 200 μm in diameter at 35°C. Plotted is the average of the peak amplitudes of nine

transducers per detector. Count rates are given per active mass. A frequency filter with a cut-off

below 18 kHz was applied. Neutron data are represented by shaded and α-data by unshaded

histograms. Det. 76 has a high α-background and the AmBe neutron source was at 10 cm

distance. The neutron calibration with det. 93 was performed with the source 1.5 m away; here

the α-background appears also in the calibration run as a shoulder at higher amplitudes.

12 New Journal of Physics

Heavy ion microprobes: a

unique tool for bystander

research and other

radiobiological applications

K O Voss, C Fournier and G Taucher-Scholz

Gesellschaft für Schwerionenforschung (GSI), Planckstrasse 1, 64291 Darmstadt,


The risk assessment for low doses of high linear energy transfer (LET) radiation

has been challenged by a growing body of experimental evidence showing

that non-irradiated bystander cells can receive signals from irradiated cells to

elicit a variety of cellular responses. These may be significant for radiation

protection but also for radiation therapy using heavy ions. Charged particle

microbeams for radiobiological application provide a unique means to

address these issues by allowing the precise irradiation of single cells with a

counted numbers of ions. Here, we focus specifically on heavy ion microbeam

facilities currently in use for biological purposes, describing their technical

features and biological results. Typically, ion species up to argon are used for

targeted biological irradiation at the vertically collimated microbeam at JAEA

(Takasaki, Japan). At the SNAKE microprobe in Munich, mostly oxygen ions

have been used in a horizontal focused beam line for cell targeting. At GSI

(Darmstadt), a horizontal microprobe with a focused beam for defined

targeting using ion species up to uranium is operational. The visualization of

DNA damage response proteins relocalizing to defined sites of ion traversal

has been accomplished at the three heavy ion microbeam facilities described

above and is used to study mechanistic aspects of heavy ion effects.

However, bystander studies have constituted the main focus of biological

applications. While for cell inactivation and effects on cell cycle progression a

response of non-targeted cells has been described at JAEA and GSI,

respectively, in part controversial results have been obtained for the induction

of DNA damage measured by double-strand formation or at the cytogenetic

level. The results emphasize the influence of the cellular environment, and

standardization of experimental conditions for cellular studies at different

facilities as well as the investigation of bystander effects in tissue will be the

aims of future research. At present, the most important conclusion of

radiobiology studies at heavy ion microbeams is that bystander responses are

not accentuated for increasing ionizing density radiation.

K O Voss et al 2008 New J. Phys. 10 075011

Single cells were targeted with 5 hits of argon ions in a cross formation. The hits were

visualized by γH2AX immunofluorescence staining (see enlarged inset).

Experimental studies of

compensation of

beam–beam effects with

Tevatron electron lenses

V Shiltsev1 , Y Alexahin1 , K Bishofberger2 , V Kamerdzhiev1 , V Parkhomchuk3 ,

V Reva3 , N Solyak1 , D Wildman1 , X-L Zhang1 and F Zimmermann4 1 Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA

2 Los Alamos National Laboratory, Los Alamos, NM 87545, USA

3 Budker INP, Novosibirsk, 630090, Russia

4 CERN, European Organization for Nuclear Research, CH-1211 Genève,


Applying the space-charge forces of a low-energy electron beam can lead

to a significant improvement of the beam-particle lifetime limit arising from

the beam–beam interaction in a high-energy collider. In this paper,

we present the results of various beam experiments with ‘electron lenses',

novel instruments developed for the beam–beam compensation at the

Tevatron, which collides 980 GeV proton and antiproton beams. We study

the dependencies of the particle betatron tunes on the electron beam

current, energy and position; we explore the effects of electron-beam

imperfections and noises; and we quantify the improvements of the

high-energy beam intensity and the collider luminosity lifetime obtained

by the action of the Tevatron electron lenses.

V Shiltsev et al 2008 New J. Phys. 10 043042

Schematic view of the transverse electron beam alignment with respect to the proton and

antiproton beams.

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New Journal of Physics: Best of 2008

The trapped twodimensional

Bose gas:

from Bose–Einstein

condensation to


Thouless physics

Z Hadzibabic1,2 , P Krüger1,3,4 , M Cheneau1 , S P Rath1 and J Dalibard1 ,5

1 Laboratoire Kastler Brossel, CNRS, École Normale Supérieure, 24 rue Lhomond,

75005, Paris, France

2 Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK

3 Kirchhoff Institut für Physik, Universität Heidelberg, 69120 Heidelberg, Germany

4 Midlands Centre for Ultracold Atoms, School of Physics and Astronomy, University

of Nottingham, Nottingham NG7 2RD, UK

We analyze the results of a recent experiment with bosonic rubidium atoms

harmonically confined in a quasi-two-dimensional (2D) geometry. In this

experiment a well-defined critical point was identified, which separates the

high-temperature normal state characterized by a single component density

distribution, and the low-temperature state characterized by a bimodal

density distribution and the emergence of high-contrast interference

between independent 2D clouds. We first show that this transition cannot

be explained in terms of conventional Bose–Einstein condensation of the

trapped ideal Bose gas. Using the local density approximation (LDA), we

then combine the mean-field (MF) Hartree–Fock theory with the prediction

for the Berezinskii–Kosterlitz–Thouless (BKT) transition in an infinite uniform

system. If the gas is treated as a strictly 2D system, the MF predictions for

the spatial density profiles significantly deviate from those of a recent

quantum Monte Carlo (QMC) analysis. However, when the residual thermal

excitation of the strongly confined degree of freedom is taken into account,

excellent agreement is reached between the MF and the QMC approaches.

For the interaction strength corresponding to the experiment, we predict a

strong correction to the critical atom number with respect to the ideal gas

theory (factor ∼2). Quantitative agreement between theory and experiment

is reached concerning the critical atom number if the predicted density

profiles are used for temperature calibration.

Z Hadzibabic et al 2008 New J. Phys. 10 045006

(a) Hybrid 3D MF prediction for the normalized column density for the lattice configuration A,

T = 150 nK and N = 110 000 atoms. For these parameters the phase space density associated

with the lowest eigenvalue of the z motion reaches the critical value D c at the center of the most

populated planes. The dotted line is a Gaussian fit which gives the effective temperature

T eff = 0.64 T = 96 nK. (b) Critical atom number as a function of the effective temperature

obtained from a Gaussian fit of the MF result.

New Journal of Physics 13

New Journal of Physics: Best of 2008

Elastic electron

scattering from


experimental and

theoretical studies

V Vizcaino 1 , J Roberts 1,2 , J P Sullivan 1 , M J Brunger 2 , S J Buckman 1 ,

C Winstead 3 and V McKoy 3

1 Centre for Antimatter-Matter Studies, AMPL, RSPhysSE, Australian National

University, 0200 Canberra, Australia

2 Centre for Antimatter-Matter Studies, SOCPES, Flinders University, GPO Box 2100,

Adelaide 5001, South Australia

3 A A Noyes Laboratory of Chemical Physics, California Institute of Technology,

Pasadena, CA 91125, USA

We report the results of measurements and calculations for elastic electron

scattering from 3-hydroxytetrahydrofuran (C 4 H 8 O 2 ). The measurements are

performed with a crossed electron-target beam apparatus and the absolute

cross-sections are determined using the relative flow technique. The

calculations are carried out using the Schwinger multichannel method in

the static-exchange plus polarization (SEP) approximation. A set of angular

differential cross-sections (DCS) is provided at five incident energies (6.5,

8, 10, 15 and 20 eV) over an angular range of 20–130°, and the energy

dependence of the elastic DCS at a scattering angle of 120° is also

presented. Integral elastic and elastic momentum transfer cross-sections

have also been derived and calculated. The results are compared with those

of recent measurements and calculations for the structurally similar

molecule tetrahydrofuran (C 4 H 8 O).

V Vizcaino et al 2008 New J. Phys. 10 053002

Absolute DCS (10 –16 cm 2 sr –1 ) shown as a function of energy at a scattering angle of 120°.

Spin squeezing in optical

lattice clocks via latticebased

QND measurements

D Meiser, Jun Ye and M J Holland

JILA, National Institute of Standards and Technology and University of Colorado,

Boulder, CO 80309-0440, USA

14 New Journal of Physics

Quantum projection noise will soon limit the best achievable precision of

optical atomic clocks based on lattice-confined neutral atoms. Squeezing

the collective atomic pseudo-spin via measurement of the clock state

populations during Ramsey

interrogation suppresses the

projection noise. We show here

that the lattice laser field can

be used to perform ideal

quantum non-demolition

measurements without clock

shifts or decoherence and

explore the feasibility of such

an approach in theory with the

lattice field confined in a ring-

Illustration of the trajectory of the atomic pseudo-spin

on the Bloch sphere during the Ramsey pulse

sequence. 1, action of the first pulse; 2, free

evolution; and 3, action of the second pulse. After

the second pulse the population difference of the

clock states is at a scattering

angle of 120°.

D Meiser et al 2008 New J. Phys. 10 073014

resonator. Detection of the

motional sideband due to the

atomic vibration in the lattice

wells can yield signal sizes a

hundredfold above the

projection noise limit.

Theory of cavity-assisted

microwave cooling of

polar molecules

Margareta Wallquist1,2 , Peter Rabl3,4 , Mikhail D Lukin3,4 and Peter Zoller1,2 1 Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria

2 Institute for Quantum Optics and Quantum Information of the Austrian Academy of

Sciences, 6020 Innsbruck, Austria

3 Institute for Theoretical Atomic, Molecular and Optical Physics, Cambridge, MA

02138, USA

4 Physics Department, Harvard University, Cambridge, MA 02138, USA

We analyze cavity-assisted cooling schemes for polar molecules in the

microwave domain, where molecules are excited on a rotational transition

and energy is dissipated via strong interactions with a lossy stripline cavity,

as recently proposed by André et al 2006 Nat. Phys. 2 636. We identify the

dominant cooling and heating mechanisms in this setup and study cooling

rates and final temperatures in various parameter regimes. In particular, we

analyze the effects of a finite environment temperature on the cooling

efficiency, and find minimal temperature and optimized cooling rate in the

strong drive regime. Further, we discuss the trade-off between efficiency of

cavity cooling and robustness with respect to ubiquitous imperfections in a

realistic experimental setup, such as anharmonicity of the trapping


Margareta Wallquist et al 2008 New J. Phys. 10 063005

A schematic illustration

of the setup considered

in this paper for

cavity-assisted cooling

of polar molecules.


Diffractive hygrochromic

effect in the cuticle of

the hercules beetle

Dynastes hercules

M Rassart1 , J-F Colomer1 , T Tabarrant2 and J P Vigneron1 1 Laboratoire de Physique du Solide, University of Namur, 61 rue de Bruxelles,

5000 Namur, Belgium

2 Laboratoire de Physique des Matériaux Electroniques, University of Namur,

61 rue de Bruxelles, 5000 Namur, Belgium

The elytra from dry specimens of the hercules beetle, Dynastes hercules

appear khaki-green in a dry atmosphere and turn black passively under high

humidity levels. New scanning electron images, spectrophotometric

measurements and physical modelling are used to unveil the mechanism of

this colouration switch. The visible dry-state greenish colouration originates

from a widely open porous layer located 3 Ìm below the cuticle surface. The

structure of this layer is three-dimensional, with a network of filamentary

strings, arranged in layers parallel to the cuticle surface and stiffening an

array of strong cylindrical pillars oriented normal to the surface.

Unexpectedly, diffraction plays a significant role in the broadband

colouration of the cuticle in the dry state. The backscattering caused by

this layer disappears when water infiltrates the structure and weakens the

refractive index differences.

M Rassart et al 2008 New J. Phys. 10 033014

(a) The Dynastes hercules is greenish with eventually black spots under normal condition of

humidity. (b) When put over ebulliant water (in order to produce a level of humidity above 80%)

the beetle presents a black colouration on all its body.

Annihilation assisted

upconversion: all-organic,

flexible and transparent

multicolour display

Tzenka Miteva1 , Vladimir Yakutkin2 , Gabriele Nelles1 and

Stanislav Baluschev2 1 Sony Deutschland GmbH, Materials Science Laboratory, Hedelfingerstrasse 61,

70327 Stuttgart, Germany

2 Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz,


In this paper, we demonstrate the first all-organic, transparent, flexible,

versatile colour displays based upon triplet–triplet annihilation assisted

photon energy upconversion in viscous polymeric matrix. The devices work

with ultra-low excitation intensities down to 20 mW cm -2 red or near-IR light.

The displays are based on metallated-porphyrin sensitizers in combination

New Journal of Physics: Best of 2008

with emitters dispersed in a transparent polymeric matrix

and are driven by galvo-scanned laser diodes. The displays have external

quantum yield as high as 3.2%. The response time can be adjusted to

specific application requirements—up to 80 Ìs allowing kHz-refreshment

rate of the displayed information. It is possible to easily tune the optical

density of the screens in order to obtain a desired transmittance for

the excitation beam. We demonstrate the ability to achieve multicolour

emission, using only one excitation source. There are practically no display

size limitations.

Tzenka Miteva et al 2008 New J. Phys. 10 103002

A flexible, UC all-organic 2D-display in operation. Dimensions, 100 × 60 mm; extruded PS-sheets

(Goodfellow GmbH, 1.2 mm thickness), frontal excitation, UC-layer—250 μm thickness, UC

system PdPh4TBP/BPEA/oligo-PS. The excitation intensity is less than 20 mW cm –2 , λ = 635 nm,

galvo-scanner sampling frequency 12 kHz.

Transmutation of

singularities in optical


Tomás Tyc1,2 and Ulf Leonhardt2,3 1 Institute of Theoretical Physics and Astrophysics, Masaryk University, Kotláfiská 2,

61137 Brno, Czech Republic

2 School of Physics and Astronomy, University of St Andrews, North Haugh, St

Andrews KY16 9SS, UK

3 Physics Department, National University of Singapore, 2 Science Drive 3,

Singapore 117542

We propose a method for eliminating a class of singularities in optical

media where the refractive index goes to zero or infinity at one or more

isolated points. Employing transformation optics, we find a refractive index

distribution equivalent to the original one that is nonsingular but shows a

slight anisotropy. In this way, the original singularity is ‘transmuted’ into

another, weaker type of singularity where the permittivity and permeability

tensors are discontinuous at one point. The method is likely to find

applications in designing and improving optical devices by making them

easier to implement or to operate in a broad band of the spectrum.

T Tyc and U Leonhardt 2008 New J. Phys. 10 115038

The Eaton lens is a perfect retroreflector. Light

(shown in red) incident from the right impinges

on the Eaton lens (blue) where it turns along an

ellipse segment and is reflected back to the

direction it came from.

The transformed Eaton lens. Equally spaced

incident light rays are nearly equally spaced

around the origin of the transformed Eaton

lens, which illustrates that the refractive-index

profile is not singular anymore.

New Journal of Physics 15

New Journal of Physics: Best of 2008

Transformation optics:

approaching broadband

electromagnetic cloaking

A V Kildishev1 , W Cai1,2 , U K Chettiar1 and V M Shalaev1 1 Birck Nanotechnology Centre, School of Electrical and Computer Engineering,

Purdue University, IN 47907, USA

2 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA

94305, USA

An approach to broadband cloaking of light waves is analysed for a

simplified case of a scaling transformation for a general cylindrical

coordinate system. The proposed approach requires metamaterials with

specifically engineered dispersion. The restriction on the signs of gradients

in the dispersion dependencies of the dielectric permittivity and the

magnetic permeability for different operational wavelengths is revealed

and is shown to cause difficulties unless additional gain-assisted

compensation for losses or electromagnetically induced transparency is

introduced in the cloaking system.

A V Kildishev et al 2008 New J. Phys. 10 115029

Simulated schematic of a cloaking system for multiple wavelengths or a finite bandwidth, with

ω 1 > ω 2 > ω 3, shown in (a), (b) and (c), respectively. The two purple circles represent the physical

boundaries the cloaking device, and the orange circle between the two refers to the inner

boundary for each operational wavelength.

Vector frequency-comb



for characterizing

metamaterials We study experimentally and theoretically the high harmonic emission from

T Ganz1,2 , M Brehm1 , H G von Ribbeck1,3 , D W van der Weide4 and

F Keilmann1,2 1 Max-Planck-Institut für Biochemie and Center for NanoScience, 82152

Martinsried, Germany

2 now with Max-Planck-Institut für Quantenoptik and Center for NanoScience,

85741 Garching, Germany

3 now with Institut für Angewandte Photophysik, Technische Universität, 01062

Dresden, Germany

4 Dept. of Electrical and Computer Engineering, University of Wisconsin, Madison,

WI 53706-1691, USA

We determine infrared transmission amplitude and phase spectra of

metamaterial samples at well-defined incidence and polarization with a

vector (‘asymmetric’) frequency-comb Fourier-transform spectrometer

(c-FTS) that uses no moving elements. The metamaterials are free-standing

metallic hole arrays; we study their resonances in the 7–13 μm and

100–1000 μm wavelength regions due both to interaction with bulk waves

(Wood anomaly) and with leaky surface plasmon polaritons (near-unity

transmittance, coupling features, and dispersion). Such complex-valued

transmission and reflection spectra can directly be used to compute a

metamaterial’s complex dielectric function, as well as its magnetic and

magnetooptical permeability functions.

T Ganz et al 2008 New J. Phys. 10 123007

16 New Journal of Physics

Optical layout of a vector THz spectrometer using the ASOPS technique. To record complex THz

amplitude and phase spectra, a trigger pulse is derived to mark the temporal overlap of the pulse

trains from both lasers, generated here by cross correlating (CC) two sample beams split off the

laser beams in a BBO crystal.


Electron wavepacket

control with elliptically

polarized laser light in high

harmonic generation from

aligned molecules

Y Mairesse1,2 , N Dudovich1,3 , J Levesque1,4 , M Yu Ivanov1 , P B Corkum1 and

D M Villeneuve1 1National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario

K1A 0R6, Canada

2Centre Lasers Intenses et Applications, Université Bordeaux I, UMR 5107 (CNRS,

Bordeaux 1, CEA), 351 Cours de la Libération, 33405 Talence Cedex, France

3Department of Physics of Complex Systems, Weizmann Institute of Science,

Rehovot 76100, Israel

4INRS–Énergie et Matériaux, 1650 boul. Lionel-Boulet, CP 1020, Varennes,

Québec, J3X 1S2 Canada

aligned samples of nitrogen and carbon dioxide, in an elliptically polarized

laser field. The ellipticity induces a lateral shift of the recombining electron

wavepacket in the generation process. We show that this effect, which is

well known from high harmonic generation (HHG) in atoms, can be useful to

maintain the plane wave approximation in the case of HHG from molecules

whose orbitals contain nodal planes. The study of the harmonic signal as a

function of molecular alignment also reveals the role of the ellipticity on the

recollision angle of the electron wavepacket, which can be used to

accurately track the position of resonances in harmonic spectra.

Y Mairesse et al 2008 New J. Phys. 10 025015

Experimental high harmonic spectra as a function of ellipticity in N 2 molecules. The vertical axis is

the wavelength axis of the spectrometer, with higher frequency towards the top. The first harmonic

is H17. Each panel corresponds to a different alignment of the molecule with respect to the

polarization of the laser field (symbolized by the black arrow on the sketches): (a) –90°, (b) –45°

and (c) 0°.

Subtracting photons from

arbitrary light fields:

experimental test of

coherent state invariance

by single-photon


A Zavatta1,2 , V Parigi2,3 , M S Kim4 , and M Bellini1,3 1Istituto Nazionale di Ottica Applicata (CNR), L.go E. Fermi, 6, I-50125, Florence,


2Department of Physics, University of Florence, I-50019 Sesto Fiorentino, Florence,


3LENS, Via Nello Carrara 1, 50019 Sesto Fiorentino, Florence, Italy

4School of Mathematics and Physics, The Queen’s University, Belfast, BT7 1NN,

United Kingdom

The operator annihilating a single quantum of excitation in a bosonic field is

one of the cornerstones for the interpretation and prediction of the behavior of

the microscopic quantum world. Here we present a systematic experimental

study of the effects of single-photon annihilation on some paradigmatic light

states. In particular, by demonstrating the invariance of coherent states by

this operation, we provide the first direct verification of their definition as

eigenstates of the photon annihilation operator.

A Zavatta et al 2008 New J. Phys. 10 123006

Scheme of the experimental implementation of conditional single-photon subtraction. A high

transmissivity beam splitter (BS) splits some light of the incident field (indicated by its density

operator ρ) towards an on/off photodetector. A click in this detector conditionally prepares the

photon-subtracted state (denoted by ρ sub) and triggers its homodyne detection.

New Journal of Physics: Best of 2008

Conditional preparation

of single photons using

parametric downconversion:

a recipe for purity

P J Mosley, J S Lundeen, B J Smith and I A Walmsley

Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK

In an experiment reported recently (Mosley et al 2008 Phys. Rev. Lett. 100

133601), we demonstrated that, through group velocity matched

parametric downconversion, heralded single photons can be generated in

pure quantum states without spectral filtering. The technique relies on

factorable photon pair production, initially developed theoretically in the

strict collinear regime; focusing—required in any experimental

implementation—can ruin this factorability. Here, we present the numerical

model used to design our single photon sources and minimize spectral

correlations in the light of such experimental considerations. Furthermore,

we show that the results of our model are in good agreement with

measurements made on the photon pairs and give a detailed description of

the exact requirements for constructing this type of source.

P J Mosley et al 2008 New J. Phys. 10 093011

An illustration of how pump spatial chirp can affect the joint spectrum in the case of a focused

pump in a potassium dihydrogen phosphate (KDP) crystal. Five discrete directions of propagation

within a continuous pump distribution are considered; (a) and (c) show positive correlation of

pump frequency with phasematching angle, (b) and (d) show negative correlation.

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New Journal of Physics 17

New Journal of Physics: Best of 2008

Imaging of carrier-envelope

phase effects in abovethreshold


with intense few-cycle

laser fields

M F Kling1,2 , J Rauschenberger2,3 , A J Verhoef2 , E Hasović 4 , T Uphues2 ,

D B Milosević 4,5 , H G Muller1 and M J J Vrakking1 1 FOM Instituut voor Atoom en Molecuul Fysica (AMOLF), Kruislaan 407, 1098 SJ

Amsterdam, Netherlands

2 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748

Garching, Germany

3 Department für Physik, Ludwig-Maximilians-Universität München, Am

Coulombwall 1, 85748 Garching, Germany

4 Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo,

Bosnia and Herzegovina

5Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany

Sub-femtosecond control of the electron emission in above-threshold

ionization of the rare gases Ar, Xe and Kr in intense few-cycle laser fields is

reported with full angular resolution. Experimental data that were obtained

with the velocity-map imaging technique are compared to simulations using

the strong-field approximation

(SFA) and full time-dependent

Schrödinger equation (TDSE)

calculations. We find a pronounced

asymmetry in both the energy and

angular distributions of the electron

emission that critically depends on

the carrier-envelope phase (CEP) of

the laser field. The potential use of

imaging techniques as a tool for

single-shot detection of the CEP is


Inverted image of above-threshold ionization in

xenon for 25 fs laser pulses at 10 14 W cm –2 .


18 New Journal of Physics

M F Kling et al 2008 New J. Phys. 10


Intense single attosecond

pulses from surface

harmonics using the

polarization gating


S G Rykovanov1,2 , M Geissler3 , J Meyer-ter-Vehn1 and G D Tsakiris1 1Max-Planck Institute für Quantenoptik, Hans-Kopfermann strasse 1, 85748,

Garching, Germany

2Moscow Physics Engineering Institute, Kashirskoe shosse 31, 115409 Moscow,


3Department of Physics and Astronomy, Queens University, Belfast, BT7 1NN, UK

Harmonics generated at solid surfaces interacting with relativistically strong

laser pulses are a promising route towards intense attosecond pulses. In

order to obtain single attosecond pulses one can use few-cycle laser pulses

with carrier-envelope phase stabilization. However, it appears feasible to

use longer pulses using polarization gating—the technique known for a long

time from gas harmonics. In this paper, we investigate in detail a specific

approach to this technique on the basis of one-dimensional-particle-in-cell

(1D PIC) simulations, applied to surface harmonics. We show that under

realistic conditions polarization gating results in significant temporal

confinement of the harmonics emission allowing thus the generation of

intense single attosecond pulses. We study the parameters needed for

gating only one attosecond pulse and show that this technique is

applicable to both normal and oblique incidence geometry.

S G Rykovanov et al 2008 New J. Phys. 10 025025

A technique for generating a pulse with time-varying ellipticity. The first crystal plate splits a

linearly polarized pulse into two delayed pulses linearly polarized in two mutually perpendicular

planes. The thickness of the plate is chosen in a such a way as to dephase the two pulses so that

the plate serves as the multiple order quarter wavelength plate The field after the first plate is

linearly polarized at the beginning and at the end and has circular polarization in the middle. The

second plate serves as a zero-order quarter wavelength plate and transforms linear polarization

into circular and vice versa.

Feasibility of electrostatic

microparticle propulsion

Th Trottenberg 1 , H Kersten 1 and H Neumann 2

1 Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-

Universität, D-24118 Kiel, Germany

2 Leibniz-Institut für Oberflächenmodifizierung, D-04318 Leipzig, Germany

This paper discusses the feasibility of electrostatic space propulsion which

uses microparticles as propellant. It is shown that particle charging in a

plasma is not sufficient for electrostatic acceleration. Moreover, it appears

technically difficult to extract charged particles out of a plasma for

subsequent acceleration without them being discharged. Two novel thruster

concepts are proposed. In the first one, particles with low secondary

electron emission are charged using energetic electrons in the order of

magnitude of 100 eV. The second concept charges the particles by contact

with needle electrodes at high electrostatic potential ( ~ 20 kV). Both

methods allow the maximum possible charges on microparticles.

Th Trottenberg et al 2008 New J. Phys. 10 063012

Calculated exhaust speeds for 0.5 μm

particles for three different charging

techniques. The specific charges are

+ 37 C kg –1 (contact charging),

-14 C kg –1 (energetic electrons) and

-2.3 C kg –1 (plasma).

Complex plasma laboratory

PK-3 Plus on the

International Space Station

H M Thomas1 , G E Morfill1 , V E Fortov2 , A V Ivlev1 , V I Molotkov2 , A M Lipaev2 ,

T Hagl1 , H Rothermel1 , S A Khrapak1 , R K Suetterlin1 , M Rubin-Zuzic1 ,

O F Petrov2 , V I Tokarev3 and S K Krikalev4 1 Max-Planck-Institut für extraterrestrische Physik, 85741 Garching, Germany

2 Institute for High Energy Densities, Russian Academy of Sciences, Moscow,


3 Yuri Gagarin Cosmonaut Training Centre, Star City, Russia

4RSC-Energia, 141070 Korolev, Russia

PK-3 Plus is the second-generation laboratory for the investigation of

complex plasmas under microgravity conditions on the International Space

Station (ISS). It has more advanced hardware, software and diagnostics

than its precursor PKE-Nefedov (Nefedov et al 2003 New J. Phys. 5 33). The

first experiments with PK-3 Plus show the perfect functioning of the

apparatus and provide much better insights into the properties of complex

plasmas. In particular, the ‘void’ in the center of the complex plasma cloud

can now be easily closed, thus providing a much better homogeneity of the

complex plasma—a feature which was hardly achievable before—but which

is essential for many precision studies. Moreover, the use of the function

generator at frequencies above the dust plasma frequency provides many

possibilities for future experiments. Other interesting phenomena are

related to high densities of the microparticles in the complex plasma. These

so-called heartbeat and filamentary mode instabilities can be investigated

in detail, by comparing particle motion with the discharge glow


H M Thomas et al 2008 New J. Phys. 10 033036

A 3D view of the symmetrically driven rf-plasma chamber. The dispensers are magnetically driven

pistons with a storage volume at their ends which is filled with microparticles and covered with a

sieve with an adapted mesh size. The microparticles are dispersed through the sieve into the

plasma chamber by electromagnetically driven strokes of the piston.

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New Journal of Physics: Best of 2008

Space and time resolved

measurements of the heating

of solids to ten million kelvin

by a petawatt laser

M Nakatsutsumi1 , J R Davies2 , R Kodama1,3 , J S Green4,5 , K L Lancaster4 ,

K U Akli6 , F N Beg7 , S N Chen7 , D Clark8 , R R Freeman8 , C D Gregory9 ,

H Habara1,3 , R Heathcote4 , D S Hey10,11 , K Highbarger8 , P Jaanimagi12 ,

M H Key10 , K Krushelnick5,13 , T Ma7 , A MacPhee10 , A J MacKinnon10 ,

H Nakamura1 , R B Stephens6 , M Storm12 , M Tampo3,14 , W Theobald12 ,

L Van Woerkom8 , R L Weber8 , M S Wei7 , N C Woolsey9 and P A Norreys4,5 1 Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka

565-0871, Japan

2 GoLP, IPFN, Instituto Superior Técnico, 1049-001 Lisboa, Portugal

3 Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka

565-0871, Japan

4 STFC Rutherford Appleton Laboratory, Chilton, Oxon, OX11 0QX, UK

5 Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7


6 General Atomics, PO Box 86508, San Diego, CA 92186-5608, USA

7 Department of Mechanical and Aerospace Engineering, University of California

San Diego, 9500 Gilman Drive 0411, La Jolla, CA 92093-0411, USA

8 Department of Physics, Ohio State University, Columbus, OH 43200-1117, USA

9 Department of Physics, University of York, Heslington, York YO10 5DD, UK

10 Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550,


11 Department of Applied Sciences, University of California, 1 Shields Avenue,

Davis, CA 95616-8254, USA

12 Laboratory of Laser Energetics, University of Rochester, 250 East River Road,

Rochester, NY 14623, USA

13 Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI

48109, USA

14 Kansai Photon Science Institute, Japan Atomic Energy Agency, Kyoto 619-0215,


The heating of plane solid targets by the Vulcan petawatt laser at powers of

0.32–0.73 PW and intensities of up to 4x10 20 W cm -2 has been diagnosed

with a temporal resolution of 17 ps and a spatial resolution of 30 μm, by

measuring optical emission from the opposite side of the target to the laser

with a streak camera. Second harmonic emission was filtered out and the

target viewed at an angle to eliminate optical transition radiation. Spatial

resolution was obtained by imaging the emission onto a bundle of fibre

optics, arranged into a one-dimensional array at the camera entrance. The

results show that a region 160 μm in diameter can be heated to a

temperature of ~10 7 K (kT/e ~ keV) in solid targets from 10 to 20 μm thick

and that this temperature is maintained for at least 20 ps, confirming the

utility of PW lasers in the study of high energy density physics. Hybrid code

modelling shows that magnetic field generation prevents increased target

heating by electron refluxing above a certain target thickness and that the

absorption of laser energy into electrons entering the solid target was

between 15–30%, and tends to increase with laser energy.

M Nakatsutsumi et al 2008 New J. Phys. 10 043046

Spatial images from the high

speed sampling camera

(HISAC) at the temporal peak

of the emission for the

thinnest and thickest targets

used: (a)


318 J, (b) Al(75)Cu(5)Al(1)

224 J.

New Journal of Physics 19

New Journal of Physics: Best of 2008


Structure of epitaxial

graphene on Ir(111)

Alpha T N’Diaye, Johann Coraux, Tim N Plasa, Carsten Busse and

Thomas Michely

II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln,


A graphene monolayer has been prepared on an Ir(111) single crystal via

pyrolytic cleavage of ethylene (C 2 H 4 ). The resulting superstructure has been

examined with scanning tunneling microscopy (STM) and low energy

electron diffraction. It has been identified as a well aligned,

incommensurate (9.32 x 9.32) pattern, which is described as a moiré. This

pattern shows three distinct regions resulting from different local

configurations of the carbon adlayer with respect to the Ir-substrate. These

regions are imaged differently by STM and differ strongly in their ability to

bind metal deposits.

Alpha T N’Diaye et al 2008 New J. Phys. 10 043033

XMCD studies on Co and Li

doped ZnO magnetic


Thomas Tietze1 , Milan Gacic2 , Gisela Schütz1 , Gerhard Jakob2 ,

Sebastian Brück1 and Eberhard Goering1 1 Max-Planck-Institute for Metal Research, Heisenbergstrasse 3, 70569 Stuttgart,


2 Institute of Physics, Johannes Gutenberg-University, 55099 Mainz, Germany

ZnO doped with a few per cent (

A new crystalline phase of

four-fold coordinated silicon

and germanium

Yoshitaka Fujimoto1,4 , Takashi Koretsune2 , Susumu Saito2 , Takashi Miyake3,4 and Atsushi Oshiyama1,4 1 Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656,


2 Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro,

Tokyo 152-8551, Japan

3 Research Institute for Computational Sciences, AIST, Umezono, Tsukuba 305-

8568, Japan

4 CREST, Japan Science and Technology Agency, Honcho, Kawaguchi, Saitama

332-0012, Japan

We have performed first-principles calculations for body-centered tetragonal

(bct) Si and Ge consisting solely of four-fold coordinated elements. The

structural optimization has been carried out based on the local density

approximation (LDA) in the density functional theory (DFT). For total-energy

minimized structures, quasi-particle spectra have been calculated using GW

approximation. We find that the bct Si and Ge are new stable crystalline

phases reachable under tensile stress with moderate magnitude. We also find

that the bct Ge is a semimetal with the carrier density of 2x10 19 cm -3,

whereas the bct Si is a semiconductor with the indirect band gap of 0.5 eV.

The calculated density of states of the bct Si and Ge show characteristic

features which are discriminated from those of the diamond structures.

Effective masses of conduction-band electrons and valence-band holes are

found to be relatively light compared with those of the diamond Si and Ge. The

origins of reduction or closure of band gaps are discussed.

Yoshitaka Fujimoto et al 2008 New J. Phys. 10 083001

Schematic view of the body-centered tetragonal phase: (a) three-dimensional view, (b) top view,

(c) side view, and (d) Brillouin zone. Dashed lines denote the rectangle unit cells. � i (i = 1, 2 and

3) and d j (j = 1 and 2) represent the corresponding bond angles and bond lengths, respectively.

New Journal of Physics: Best of 2008

Onset of magnetic order in

strongly-correlated systems

from ab initio electronic

structure calculations:

application to transition

metal oxides

I D Hughes 1 , M Däne 2,3 , A Ernst 2 , W Hergert 3 , M Lüders 4 , J B Staunton 1 ,

Z Szotek 4 and W M Temmerman 4

1 Department of Physics, University of Warwick, Coventry, CV4 7AL, UK

2 Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany

3 Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Friedemann-Bach-

Platz 6, D-06099 Halle, Germany

4 Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK

We describe an ab initio theory of finite temperature magnetism in stronglycorrelated

electron systems. The formalism is based on spin density

functional theory, with a self-interaction corrected local spin density

approximation (SIC-LSDA). The self-interaction correction is implemented

locally, within the Kohn–Korringa–Rostoker (KKR) multiple-scattering method.

Thermally induced magnetic fluctuations are treated using a mean-field

‘disordered local moment’ (DLM) approach and at no stage is there a fitting to

an effective Heisenberg model. We apply the theory to the 3d transition metal

oxides, where our calculations reproduce the experimental ordering

tendencies, as well as the qualitative trend in ordering temperatures. We find

a large insulating gap in the paramagnetic state which hardly changes with

the onset of magnetic order.

I D Hughes et al 2008 New J. Phys. 10 063010

The local density of states (DOS) for MnO in its paramagnetic (DLM) state on Mn (full line) and O

sites (dashed). The upper (lower) panel shows the DOS associated with electrons with spins

parallel (anti-parallel) to the local moment on the site.

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New Journal of Physics 21

New Journal of Physics: Best of 2008


Single atoms on an

optical nanofibre

K P Nayak and K Hakuta

Department of Applied Physics and Chemistry, University of Electro-

Communications, Chofu, Tokyo 182-8585, Japan

We show that single atoms can be detected using a sub-wavelength-diameter

silica-fibre, an optical nanofibre, and the fact that single photons

spontaneously emitted from the atoms can be readily guided into a singlemode

optical fibre. Moreover, we find that single atoms around the nanofibre

reveal a very prominent spectral feature, that is, the excitation spectrum splits

into two peaks with a very small separation, smaller than the natural linewidth.

K P Nayak and K Hakuta 2008 New J. Phys. 10 053003

Nanoscale superconducting

properties of amorphous

W-based deposits grown

with a focused-ion-beam

I Guillamón1 , H Suderow1 , S Vieira1 , A Fernández-Pacheco2,3,4 , J Sesé2,4, R Córdoba2,4 , J M De Teresa3,4 and M R Ibarra2,3,4 1 Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia

Condensada Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de

Ciencias Universidad Autónoma de Madrid, E-28049 Madrid, Spain

2 Instituto de Nanociencia de Aragón, Universidad de Zaragoza, Zaragoza 50009,


3 Instituto de Ciencia de Materiales de Aragón, Facultad de Ciencias, Universidad

de Zaragoza-CSIC, Zaragoza 50009, Spain

4 Departamento de Física de la Materia Condensada, Universidad de Zaragoza,

Zaragoza 50009, Spain

We present very low temperature scanning tunneling microscopy and

spectroscopy (STM/S) measurements in W-based amorphous

superconducting nanodeposits grown using a metal–organic precursor and a

focused-ion-beam. The superconducting gap closely follows s-wave

Bardeen–Cooper– Schrieffer theory, and STS images under magnetic fields

show a hexagonal vortex lattice whose orientation is related to features

observed in the topography through STM. Our results demonstrate that the

superconducting properties at the surface of these deposits are very

homogeneous, down to atomic scale.

I Guillamón et al 2008 New J. Phys. 10 093005

22 New Journal of Physics

The fluorescence excitation

spectra (solid curve)

measured through the

nanofibre under one singleatom

condition for a probe

laser intensity of

7 mW cm –2 . Detuning is

measured with respect to

the atomic resonance. The

dashed curve shows the

theoretically calculated

spectra assuming a V-type

three-level scheme.

Images of the Abrikosov vortex lattice of the W-based nanodeposit under a magnetic field of 1T as

observed with STM.

Nanoelectromechanics of

suspended carbon


A K Hüttel, M Poot, B Witkamp and H S J van der Zant

Molecular Electronics and Devices, Kavli Institute of Nanoscience, Delft University

of Technology, PO Box 5046, 2600 GA Delft, The Netherlands

We discuss different types of measurements targetting the interplay of

mechanical motion with electrical transport in suspended single-wall carbon

nanotube devices. In driven resonator experiments, the transversal acoustical

vibration mode is detected and identified at room temperature using ac downmixing

techniques. In contrast, low-temperature transport spectroscopy

enables the observation of the longitudinal acoustic mode in the quantum

limit in single electron tunnelling. This vibrational excitation can also be

observed in higher order tunnelling current for appropriate electronic coupling

to the leads. Experimental roads towards the quantum limit of the transversal

vibration mode—as ultimate quantum-limited beam resonator—are explored,

e.g. extending both abovementioned measurement techniques.

A K Hüttel et al 2008 New J. Phys. 10 095003

Differential conductance of

a single electron tunnelling

device based on a

suspended carbon

nanotube. The Coulomb

blockade dominates

transport although a large

number of strongly

gate-dependent inelastic

co-tunnelling resonances

is also observed.


renormalization and

enhancement of Coulomb


M Durach1 , A Rusina1 , V I Klimov2 and M I Stockman1,3 1 Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA

2 Chemistry Division, C-PCS, Los Alamos National Laboratory, Los Alamos, NM,


3 On sabbatical leave as an Invited Professor at l’Institut d’Alembert, Ecole Normale

Sup⁄ieure de Cachan, 94235-Cachan, France.

In this paper, we propose a general and powerful theory of the plasmonic

enhancement of the many-body phenomena resulting in a closed expression

for the surface plasmon-dressed Coulomb interaction. We illustrate this theory

by computing the dressed interaction explicitly for an important example of

metal–dielectric nanoshells which exhibits a rich resonant behavior in

magnitude and phase. This interaction is used to describe the

nanoplasmonic-enhanced Förster resonant energy transfer (FRET) between

nanocrystal quantum dots near a nanoshell.

M Durach et al 2008 New J. Phys. 10 105011

Schematic of a metal nanostructure and semiconductor nanocrystal quantum dots (NQDs)

situated in its vicinity. The metal nanostructure is depicted by the dark blue color. Two electrons

are indicated in the NQDs by the blue color and the local plasmonic fields are schematically

shown by the orange color.


The shortcomings of semilocal

and hybrid functionals:

what we can learn from

surface science studies

A Stroppa and G Kresse

Faculty of Physics, University of Vienna, and Center for Computational Materials

Science, Sensengasse 8/12, A-1090 Vienna, Austria

A study of the adsorption of CO on late 4d and 5d transition metal (111)

surfaces (Ru, Rh, Pd, Ag, Os, Ir and Pt) considering atop and hollow site

adsorption is presented. The applied functionals include the gradientcorrected

Perdew–Burke–Ernzerhof (PBE) and Becke–Lee–Yang–Parr (BLYP)

functionals, and the corresponding hybrid Hartree–Fock density functionals

HSE and B3LYP. We find that PBE-based hybrid functionals (specifically HSE)

yield, with the exception of Pt, the correct site order on all considered metals,

but they also considerably overestimate the adsorption energies compared to

experiment. On the other hand, the semi-local BLYP functional and the

corresponding hybrid functional B3LYP yield very satisfactory adsorption

energies and the correct adsorption site for all surfaces. We are thus faced

with a Procrustean problem: the B3LYP and BLYP functionals seem to be the

overall best choice for describing adsorption on metal surfaces, but they

simultaneously fail to account well for the properties of the metal, vastly

overestimating the equilibrium volume and underestimating the atomization

energies. Setting out from these observations, general conclusions are drawn

on the relative merits and drawbacks of various semi-local and hybrid

functionals. The discussion includes a revised version of the PBE functional

specifically optimized for bulk properties and surface energies (PBEsol), a

revised version of the PBE functional specifically optimized to predict accurate

adsorption energies (rPBE), as well as the aforementioned BLYP functional.

We conclude that no semi-local functional is capable of describing all aspects

properly, and including non-local exchange also only improves some but

worsens other properties.

A Stroppa and G Kresse 2008 New J. Phys. 10 063020

New Journal of Physics: Best of 2008

A finite-difference time-domain (FDTD) simulation of the (EM) field distribution originated from

p-polarized back-side illumination of a sub-wavelength slit on a thick Au film.

Modulation of surface

plasmon coupling-in by

one-dimensional surface


F López-Tejeira1 , Sergio G Rodrigo1 , L Martín-Moreno1 , F J García-Vidal2 ,

E Devaux3 , J Dintinger3,7 , T W Ebbesen3 , J R Krenn4 , I P Radko5 ,

S I Bozhevolnyi5 , M U González6,8 , J C Weeber6 and A Dereux6 1 Departamento de Física de la Materia Condensada, Facultad de Ciencas-ICMA,

Universidad de Zaragoza-CSIC, E-50009 Zaragoza, Spain

2 Departamento de Física Teórica de la Materia Condensada, Universidad

Autónoma de Madrid, E-28049 Madrid, Spain

3 Laboratoire de Nanostructures, ISIS, Université Louis Pasteur, F-67000

Strasbourg, France

4 Institute of Physics, Karl Franzens University, A-8010 Graz, Austria

5 Department of Physics and Nanotechnology, Aalborg University, DK-9220

Aalborg, Denmark

6 Laboratoire de Physique de l’Université de Bourgogne, UMR CNRS 5027, F-

21078 Dijon, France

7 Present address: Nanophotonics and Metrology Laboratory, Swiss Federal

Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland.

8 Present address: ICFO-Institut de Cincies Fotniques, E-08860 Castelldefels,


Difference between the PBE and HSE charge

density for Rh and Pt bare surfaces plotted in a

(111)-plane ~ 0.7 Å above the surface plane. Red

(blue) color corresponds to regions where the PBE

charge density is larger (smaller) than the HSE

one. Three isolines are drawn to guide the eye.

‘fcc’ and ‘hcp’ indicate the locations of the fcc and

hcp hollow sites, respectively.

F López-Tejeira et al 2008 New J. Phys. 10 033035

Surface plasmon-polaritons have

recently attracted renewed interest

in the scientific community for their

potential in sub-wavelength optics,

light generation and nondestructive

sensing. Given that

they cannot be directly excited by

freely propagating light due to their

intrinsic binding to the metal

surface, the light–plasmon

coupling efficiency becomes of

crucial importance for the success

of any plasmonic device. Here, we

present a comprehensive study on

the modulation (enhancement or

suppression) of such a coupling

efficiency by means of onedimensional

surface corrugation.

Our approach is based on simple

wave interference and enables us

to make quantitative predictions

which have been experimentally

confirmed at both the near-infrared

and telecom ranges.

New Journal of Physics 23

New Journal of Physics: Best of 2008

On the internal energy

of sputtered clusters

A Wucher 1 , C Staudt 1 , S Neukermans 2 , E Janssens 2 , F Vanhoutte 2 ,

E Vandeweert 2 , R E Silverans 2 and P Lievens 2

1 Fachbereich Physik, Universität Duisburg-Essen, D-47048 Duisburg, Germany

2 Laboratorium voor Vaste-Stoffysica en Magnetisme, K U Leuven, Celestijnenlaan

200d—bus 2414, B-3001 Leuven, Belgium

We have used laser ionization and time-of-flight mass spectrometry to

investigate the internal excitation of neutral clusters that were generated by

sputtering from a solid indium surface under bombardment with 15 keV Xe +

ions. More specifically, single photon ionization of the clusters is

accomplished by a tunable, frequency doubled laser and the photoionization

efficiency (PIE) curves are collected with the photon energy varied around the

ionization energy in a range between 4.2–6 eV. The results are compared with

the PIE curves of supposedly cold indium clusters which were produced by a

supersonic nozzle expansion using a laser vaporization source and

investigated under otherwise similar conditions. As a result, the sputtered

clusters show a distinctive broadening and shift of the PIE curve in the

threshold region, thus illustrating the influence of the sputtering process in

increasing the internal energy of the ejected clusters. The experimental PIE

curves are interpreted in terms of a simple model using the internal

temperature and ionization energy of the cluster as fit parameters. Depending

on the cluster size, temperatures between 3850 and about 1000 K are found

for sputtered In n clusters.

A Wucher et al 2008 New J. Phys. 10 103007

Comparison of measured and modelled photoionization efficiency (PIE) curve of sputtered

neutral In 13 clusters. Dots: experimental data; lines: least squares fit.

24 New Journal of Physics

Surface structure of

Sn-doped In 2 O 3 (111)

thin films by STM

E H. Morales 1 , Y He 1 , M Vinnichenko 2 , B Delley 3 and U Diebold 1

1 Department of Physics, Tulane University, New Orleans, Louisiana 70118, USA

2 Institut für Ionenstrahlphysik und Materialforschung, Forschungszentrum

Dresden-Rossendorf, Postfach 510119, D-01314 Dresden, Germany

3 Paul-Scherrer-Institut, HGA/123, CH-5232 Villigen, Switzerland

High-quality Sn-doped In 2O 3 (ITO) films were grown epitaxially on yttria

stabilized zirconia (111) with oxygen-plasma assisted MBE. The 12-nm thick

films, containing 2–6 % Sn, are fully-oxidized. Angle-resolved XPS confirms

that the Sn dopant substitutes In atoms in the bixbyite lattice. From the

analysis of the plasmon loss in XPS core level peaks, taken from a film with

6 at.% Sn content, it is estimated that ~ 1/3 of the Sn atom are electrically

active. RHEED shows a flat surface morphology and STM shows terraces

several hundred nanometers in width. The terraces consist of ~ 10 nm wide

orientational domains, which is attributed to the initial nucleation of the film.

LEED and STM results show a bulk-terminated (1 x 1) surface, which is

supported by first-principles DFT calculations. Atomically-resolved STM

images are consistent with Tersoff-Hamann calculations that show that

surface In atoms are imaged bright or dark, depending on the configuration of

their O neighbors. The coordination of surface atoms on the In 2O 3(111)-1x1

surface is analyzed in terms of their likely role in surface chemical reactions.

Erie H Morales et al 2008 New J. Phys. 10 125030


Ball-stick model of In 2 O 3

(111) surface (1 x 1) terminated.

Arrows mark In and O atoms with

their corresponding coordination

(a) top view where the unit cell

is marked with a broken line and

(b) side view.

Self-organization and the

selection of pinwheel

density in visual cortical


Matthias Kaschube1,2,3,4 , Michael Schnabel1,2 and Fred Wolf1,2 1 Max Planck Institute for Dynamics and Self-Organization, Goettingen, Germany

2 Bernstein Center for Computational Neuroscience, Goettingen, Germany

3 Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ,


4 Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ, USA

Self-organization of neural circuitry is an appealing framework for

understanding cortical development, yet its applicability remains

unconfirmed. Models for the self-organization of neural circuits have been

proposed, but experimentally testable predictions of these models have been

less clear. The visual cortex contains a large number of topological point

defects, called pinwheels, which are detectable in experiments and therefore

in principle well suited for testing predictions of self-organization empirically.

Here, we analytically calculate the density of pinwheels predicted by a pattern

formation model of visual cortical development. An important factor

controlling the density of pinwheels in this model appears to be the presence

of non-local long-range interactions, a property which distinguishes cortical

circuits from many non-living systems in which self-organization has been

studied. We show that in the limit where the range of these interactions is

infinite, the average pinwheel density converges to �. Moreover, an average

pinwheel density close to this value is robustly selected even for intermediate

interaction ranges, a regime arguably covering interaction ranges in a wide

range of different species. In conclusion, our paper provides the first direct

theoretical demonstration and analysis of pinwheel density selection in

models of cortical self-organization and suggests quantitatively probing this

type of prediction in future high-precision experiments.

Matthias Kaschube et al 2008 New J. Phys. 10 015009

A pattern of orientation columns and long-range horizontal connections in the primary visual

cortex of tree shrew visualized using optical imaging of intrinsic signals. Long-range horizontal

connections extend over several millimetres parallel to the cortical surface (tree shrew,

superimposed on the orientation preference map). White symbols indicate locations of cells that

were filled by a tracer (biocytin); labeled axons are indicated by black symbols.

Emergence of agent swarm

migration and vortex

formation through inelastic


D Grossman 1 , I S Aranson 2 and E Ben Jacob 1,3

1 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact

Sciences, Tel-Aviv University, Tel Aviv 69978, Israel

2 Materials Science Division, Argonne National Laboratory, 9700 South Cass

Avenue, Argonne, IL 60439, USA

3 Center for Theoretical Biological Physics, University of California at San Diego, La

Jolla, CA 92093-0319, USA

Biologically inspired models of self-propelled interacting agents display a

wide variety of collective motion such as swarm migration and vortex

formation. In these models, active interactions among agents are typically

included such as velocity alignment and cohesive and repulsive forces that

represent agents’ short- and long-range ‘sensing’ capabilities of their

environment. Here, we show that similar collective behaviors can emerge in a

New Journal of Physics: Best of 2008

minimal model of isotropic agents solely due to a passive mechanism—

inelastic collisions among agents. The model dynamics shows a gradual

velocity correlation build-up into the collective motion state. The model

displays a discontinuous transition of collective motion with respect to noise

and exhibits several collective motion types such as vortex formation, swarm

migration and also complex spatio-temporal group motion. This model

can be regarded as a hybrid model, connecting granular materials and

agent-based models.

D Grossman et al 2008 New J. Phys. 10 023036

Reflecting boundary systems. Vortex formation in round boundaries with N = 900, normal

restitution coefficient r = 0.97 and density d = 0.8. Left: agent instantaneous positions; middle:

agent position traces during a small time period. Right: coarse graining velocity average.

Visualization of spiral and

scroll waves in simulated

and experimental cardiac


E M Cherry and F H Fenton

Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA

and Max Planck Institute for Dynamics and Self-organization, Göttingen, Germany

The heart is a nonlinear biological system that can exhibit complex electrical

dynamics, complete with period-doubling bifurcations and spiral and scroll

waves that can lead to fibrillatory states that compromise the heart’s ability to

contract and pump blood efficiently. Despite the importance of understanding

the range of cardiac dynamics, studying how spiral and scroll waves can

initiate, evolve, and be terminated is challenging because of the complicated

electrophysiology and anatomy of the heart. Nevertheless, over the last two

decades advances in experimental techniques have improved access to

experimental data and have made it possible to visualize the electrical state of

the heart in more detail than ever before. During the same time, progress in

mathematical modeling and computational techniques has facilitated using

simulations as a tool for investigating cardiac dynamics. In this paper, we

present data from experimental and simulated cardiac tissue and discuss

visualization techniques that facilitate understanding of the behavior of

electrical spiral and scroll waves in the context of the heart. The paper

contains many interactive media, including movies and interactive two- and

three-dimensional Java applets.

E M Cherry and F H Fenton 2008 New J. Phys. 10 125016

Visualization of a human

torso with heart in

ventricular fibrillation.

The multimedia that

accompanies the article

illustrates in 3D the

complex electrical

dynamics resulting from

multiple reentrant waves

(spiral waves) that render

the heart unable to pump.

New Journal of Physics 25

New Journal of Physics: Best of 2008

The stochastic dance of

circling sperm cells: sperm

chemotaxis in the plane

B M Friedrich and F Jülicher

Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Straße 38,

01187 Dresden, Germany

Biological systems such as single cells must function in the presence of

fluctuations. It has been shown in a two-dimensional experimental setup that

sea urchin sperm cells move towards a source of chemoattractant along

planar trochoidal swimming paths, i.e. drifting circles. In these experiments, a

pronounced variability of the swimming paths is observed. We present a

theoretical description of sperm chemotaxis in two dimensions which takes

fluctuations into account. We derive a coarse-grained theory of stochastic

sperm swimming paths in a concentration field of chemoattractant.

Fluctuations enter as multiplicative noise in the equations for the sperm

swimming path. We discuss the stochastic properties of sperm swimming and

predict a concentration-dependence of the effective diffusion constant of

sperm swimming which could be tested in experiments.

B M Friedrich and F Jülicher 2008 New J. Phys. 10 123025

Diffusion constant D of sperm swimming circles as a function of concentration c 0 for a

homogeneous concentration field of chemoattractant. Shown are simulation results (symbols)

and our analytical result (solid line). The dotted line represents the analytic value for the diffusion

constant in the absence of chemoattractant.


Complex network analysis

of state spaces for random

Boolean networks

Amer Shreim1 , Andrew Berdahl1 , Vishal Sood1,2 , Peter Grassberger1,2 and Maya Paczuski1 1 Complexity Science Group, Department of Physics and Astronomy, University of

Calgary, Calgary, AB, T2N 1N4, Canada

2 Institute for Biocomplexity and Informatics, University of Calgary, Calgary, AB, T2N

1N4, Canada

We apply complex network analysis to the state spaces of random Boolean

networks (RBNs). An RBN contains N Boolean elements each with K inputs. A

directed state space network (SSN) is constructed by linking each dynamical

state, represented as a node, to its temporal successor. We study the

26 New Journal of Physics

heterogeneity of these SSNs at both local and global scales, as well as

sample to-sample fluctuations within an ensemble of SSNs. We use indegrees

of nodes as a local topological measure, and the path diversity

(Shreim A et al 2007 Phys. Rev. Lett. 98 198701) of an SSN as a global

topological measure. RBNs with 2 ≤ K ≤ 5 exhibit non-trivial fluctuations at

both local and global scales, while K = 2 exhibits the largest sample-tosample

(possibly non-self-averaging) fluctuations. We interpret the observed

‘multi scale’ fluctuations in the SSNs as indicative of the criticality and

complexity of K = 2 RBNs. ‘Garden of Eden’ (GoE) states are nodes on an SSN

that have in-degree zero. While in-degrees of non-GoE nodes for K > 1 SSNs

can assume any integer value between 0 and 2N, for K = 1 all the non-GoE

nodes in a given SSN have the same in-degree which is always a power of two.

Amer Shreim et al 2008 New J. Phys. 10 013028

One connected cluster of an state space network for random Boolean networks with the number

of Boolean elements, N, equal to 9 and different numbers of randomly chosen input elements, K.

Nodes on the attractors are drawn in red; the other colors indicate distance from the attractor. For

instance, for K = 1, green nodes are distance one from the attractor, blue nodes are distance two

and magenta nodes are distance three. Note that for K = 1 all nodes are either GoE states or hubs

with all the hubs having the same in-degree. RM stands for a random map.

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Traffic jams without

bottlenecks —

experimental evidence for

the physical mechanism of

the formation of a jam

Yuki Sugiyama1 , Minoru Fukui2 , Macoto Kikuchi3 , Katsuya Hasebe4 , Akihiro

Nakayama5 , Katsuhiro Nishinari6,7 , Shin-ichi Tadaki8 and Satoshi Yukawa9 1 Department of Complex Systems Science, Nagoya University, Nagoya 464-8601,


2 Nakanihon Automotive College, Sakahogi 505-0077, Japan

3 Cybermedia Center, Osaka University, Toyonaka 560-0043, Japan

4 Aichi University, Miyoshi 470-0296, Japan

5 Faculty of Science and Technology, Meijo University, Nagoya 468-8502, Japan

6 Department of Aeronautics and Astronautics, The University of Tokyo, Bunkyo

113-8656, Japan

7 PRESTO, Japan Science and Technology Agency

8 Computer and Network Center, Saga University, Saga 840-8502, Japan

9 Department of Earth and Space Science, Osaka University, Toyonaka 560-0043,


A traffic jam on a highway is a very familiar phenomenon. From the physical

viewpoint, the system of vehicular flow is a non-equilibrium system of

interacting particles (vehicles). The collective effect of the many-particle

system induces the instability of a free flow state caused by the enhancement

of fluctuations, and the transition to a jamming state occurs spontaneously if

the average vehicle density exceeds a certain critical value. Thus, a bottleneck

is only a trigger and not the essential origin of a traffic jam. In this paper, we

present the first experimental evidence that the emergence of a traffic jam is a

collective phenomenon like ‘dynamical’ phase transitions and pattern

formation in a non-equilibrium system. We have performed an experiment on

a circuit to show the emergence of a jam with no bottleneck. In the initial

condition, all the vehicles are moving, homogeneously distributed on the

circular road, with the same velocity. The average density of the vehicles is

prepared for the onset of the instability. Even a tiny fluctuation grows larger

and then the homogeneous movement cannot be maintained. Finally, a jam

cluster appears and propagates backward like a solitary wave with the same

speed as that of a jam cluster on a highway.

Yuki Sugiyama et al 2008 New J. Phys. 10 033001

A snapshot from the movie of the experiment on a circular road. The circumference is 230 m, and

the number of vehicles is 22. A 360-degree video camera is situated at the center of the circle for


New Journal of Physics: Best of 2008

Specialization and herding

behavior of trading firms in

a financial market

Fabrizio Lillo1,2,3 , Esteban Moro4 , Gabriella Vaglica1,3 and Rosario N

Mantegna1,3 1 Dipartimento di Fisica e Tecnologie Relative, Università di Palermo, Viale delle

Scienze, I-90128 Palermo, Italy

2 Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA

3 CNR-INFM, Unità Operativa di Roma, Centro di Ricerca e Sviluppo SOFT, Roma,


4 Grupo Interdisciplinar de Sistemas Complejos (GISC), Departamento de

Matemáticas, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-

28911 Leganés, Spain

Agent-based models of financial markets usually make assumptions about

agent’s preferred stylized strategies. Empirical validations of these

assumptions have not been performed so far on a full-market scale. Here we

present a comprehensive study of the resulting strategies followed by the

firms which are members of the Spanish Stock Exchange. We are able to show

that they can be characterized by a resulting strategy and classified in three

well-defined groups of firms. Firms of the first group have a change of

inventory of the traded stock which is positively correlated with the

synchronous stock return whereas firms of the second group show a negative

correlation. Firms of the third group have an inventory variation uncorrelated

with stock return. Firms tend to stay in the same group over the years

indicating a long term specialization in the strategies controlling their

inventory variation. We detect a clear asymmetry in the Granger causality

between inventory variation of firms and stock return. We also detect herding

in the buying and selling activity of firms. The herding properties of the two

groups are markedly different and consistently observed over a four-year

period of trading. Firms of the second group herd much more frequently than

the ones of the first group. Our results can be used as an empirical basis for

agent-based models of financial markets.

Fabrizio Lillo et al 2008 New J. Phys. 10 043019

The thin brown line is the daily closure price of Telefónica stock for the January 2001–December

2004 time period. The three panels refer to reversing (a), uncategorized (b) and trending (c)

firms. Red circles indicate buying herding days whereas blue circles indicate selling herding days.

New Journal of Physics 27

New Journal of Physics: Best of 2008

Third quantization: a

general method to solve

master equations for

quadratic open Fermi


Tomaz˘ Prosen

Department of Physics, FMF, University of Ljubljana, Jadranska 19, SI-1000

Ljubljana, Slovenia

The Lindblad master equation for an arbitrary quadratic system of n fermions

is solved explicitly in terms of diagonalization of a 4n x4n matrix, provided

that all Lindblad bath operators are linear in the fermionic variables. The

method is applied to the explicit construction of non-equilibrium steady

states (NESS) and the calculation of asymptotic relaxation rates in the far

from equilibrium problem of heat and spin transport in a nearest neighbour

Heisenberg XY spin-1/2 chain in a transverse magnetic field.

Tomaz˘ Prosen 2008 New J. Phys. 10 043026

Complete spectrum of 212 complex eigenvalues of Liouvillean for a transverse Ising chain with

n = 6 spins and J = 1.5 and h = 1, and bath couplings � L 1 = 1, � L 2 = 0.6, � R 1 = 1 and � L 2 = 0.3.

Heat conduction and

Fourier’s law in a class of

many particle dispersing


Pierre Gaspard and Thomas Gilbert

Center for Nonlinear Phenomena and Complex Systems, Université Libre de

Bruxelles, C P 231, Campus Plaine, B-1050 Brussels, Belgium

We consider the motion of many confined billiard balls in interaction and

discuss their transport and chaotic properties. In spite of the absence of mass

transport, due to confinement, energy transport can take place through binary

collisions between neighbouring particles. We explore the conditions under

which relaxation to local equilibrium occurs on timescales much shorter than

that of binary collisions, which characterize the transport of energy, and

subsequent relaxation to local thermal equilibrium. Starting from the pseudo-

Liouville equation for the time evolution of phase-space distributions, we

derive a master equation which governs the energy exchange between the

system constituents. We thus obtain analytical results relating the transport

28 New Journal of Physics

coefficient of thermal conductivity to the frequency of collision events and

compute these quantities. We also provide estimates of the Lyapunov

exponents and Kolmogorov–Sinai entropy under the assumption of scale

separation. The validity of our results is confirmed by extensive numerical


P Gaspard and T Gilbert 2008 New J. Phys. 10 103004

Example of lattice billiards with triangular tiling. The coloured particles move among an array of

fixed black discs. The radii of both fixed and mobile discs are chosen so that (i) every moving

particle is geometrically confined to its own billiard cell, but (ii) can nevertheless exchange energy

with the moving particles in the neighbouring cells through binary collisions. The solid broken

lines show the trajectories of the moving particles centres about their respective cells. The colours

are coded according to the kinetic temperatures of the particles (from blue to red with increasing


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