Activity Report 2010 - CNRS

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THE NÉEL IRAM KIDS ARRAYS (NIKA) The Institut Néel is coordinating the NIKA collaboration, which is developing a new instrument for the 30-m IRAM (Institut de Radio Astronomie Millimetrique) telescope at Pico Veleta, near Granada (Spain). The peculiarity of this project is the use, in the focal plane, of large arrays of the new Kinetic Inductance Detectors (KIDs). the first technical run in Pico Veleta took place already in October 2009, with very encouraging results. We could observe, for example, a number of faint galactic and extra-galactic sources. The LEKID array used at the telescope in 2009 has been fabricated at the PTA-Grenoble platform. HIGHLIGHT : NANO-CHARACTERIZATION AND METROLOGY CONTACTS monfardini@grenoble.cnrs.fr alain.benoit@grenoble.cnrs.fr FURTHER READING A. Monfardini et al., Astronomy and Astrophysics, 521, id.A29 (2010) L. Swenson et al., Applied Physics Letters, 96, Issue 26, id. 263511 (2010). A. Monfardini et al., The Astrophysioal Journal, in press (2011), arXiv:1102.0870v2 KIDS development The importance of millimeter and submillimeter astronomy is rapidly increasing. In particular, three main areas of millimeter continuum research have motivated the rapid development of new technologies: 1. The study of the cold star-forming regions in the Galaxy 2. The investigation of high-redshift galaxies, dimmed in higher energy bands 3. Cosmic Microwave Background (CMB) and its anomalies (e.g. SZ effect) The Néel IRAM KIDs Arrays (NIKA) project was kicked off in November 2008. The international collaboration, led by the Institut Néel, includes Institutions in the UK (University of Cardiff), Holland (SRON), Italy (Università di Roma) and of course France (Institut Néel, IRAM- Grenoble, LPSC, LAOG). NIKA, in its final configuration, uses, in the focal plane, thousands pixels arrays of KIDs (Kinetic Inductance Detectors). A KID consist basically in a planar superconducting resonator sensitive, through changes in the film kinetic inductance, to incoming mm-wave radiation. The development of KIDs detectors in France started in 2008 in Grenoble thanks to a “Jeunes Entrants” project titled “A DC-to-THz cryogenic platform for new generations of nano-detectors”. The project was funded by the “Fondation Nanosciences” Grenoble for the period 2008-2011. In particular, Dr. Loren Swenson, post-doc hired by the Foundation, boosted incredibly the project with his pre-existing competences in RF electronics. In 2009, we started investigating a particular KID concept known as LEKID (Lumped Element KID), allowing a purely planar design and a good optical coupling. Totally unexplored at that time, we realized immediately the potential of this new configuration for future large instruments operating in the mm-wave range. Thanks to the rapid development, Fig. 1: The giant IRAM telescope, located at 2900m on the Sierra Nevada, south of Spain [Credits L.Swenson]. Insets: Alessandro MONFARDINI (top), Loren SWENSON (bottom left) and Christian HOFFMANN (bottom right). In 2010 we have further developed the first NIKA prototype to build a new, dualband instrument able to observe simultaneously at the wavelengths of 2mm (150GHz) and 1.25mm (240GHz). Fig. 2: The Crab observed by NIKA in October 2010 from the 30-m telescope. A new observational run with the improved system, and including two KIDs arrays of respectively 144 and 256 pixels has been carried out in October 2010. Thanks to the larger number of pixels, the two colors and the three-fold improvement in the detectors sensitivity, a large number of galactic and extragalactic extended sources have been detected during the six days on the sky. NIKA is today the state-of-the art concerning KIDs-based experiments, and this encourages us in proposing a multithousands pixels resident instrument, based on kinetic inductance detectors, at Pico Veleta. 11
SCANNING GATE NANOELECTRONICS In the framework of Vincent Bayot’s Chair of Excellence, two major results were obtained by scanning gate microscopy (SGM): a theoretical understanding of SGM images in the coherent regime of transport both in the presence of defects and weak magnetic field; and the discovery of Coulomb islands in a quantum Hall interferometer. In the quantum Hall (QH) regime, near integer Landau level filling factors, electrons should be perfectly transmitted through spatially separated edge states (Fig. 2). SGM uses the electrically polarized tip of a low-temperature AFM to scan above a semiconductor device while the conductance changes, due to the tip perturbation, are simultaneously mapped in real space. Previously, we have applied the SGM technique to InGaAs-based quantum rings (QRs) at low temperature and under the effect of an external magnetic field (Hackens et al., Nature Phys 2006, Martins et al., PRL 2007). When the AFM tip scans over the QR surface, fringes are observed in the tip-induced conductance changes which are essentially radial with the QR. To understand the physics behind SGM experiments, we have focused on the correspondence between the local density of states (LDOS) and SGM conductance images by including an external magnetic field in the simulations. We also generate a realistic potential profile to account for disorder, and include many conduction channels contributing to the transport. We find that, in contrast with the current density distribution, the LDOS can often be determined by recursive semi-classical trajectories with energies close to the Fermi energy. As a result, the correspondence between LDOS and SGM images is clearly established (Fig. 1). Fig. 2: An artist’s view of edge states in the quantum ring confining potential. The tip (in green) induces a local perturbation of the potential that can be scanned over the quantum Hall interferometer. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models (Rosenow et al., PRL 2007) put forward the theory that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands, giving rise to a new kind of Coulomb blockade effect. We have used SGM to demonstrate the presence of QH Coulomb islands, and reveal the spatial structure of transport inside a QH interferometer. The locations of electron islands are found by modulating the tunneling between edge states and confined electron orbits, i.e. the SGM polarized tip is used to modulate Coulomb blockade, resulting in concentric fringes surrounding the active island (Fig. 3). HIGHLIGHT : NANO-CHARACTERIZATION AND METROLOGY Fig. 1: Comparison between the LDOS (A) and conductance variation images (B) when negatively charged defects are included in the system. Moreover, by varying the Fermi level and magnetic field strength, we find that the LDOS and conductance images are periodical with the external field and that they bear the same periodicity as the Aharonov-Bohm effect. This finding strengthens our view that SGM in the weak tip-potential limit is the analogue of STM for imaging the electronic LDOS in buried open mesoscopic systems. Fig. 3: SGM image in the QH regime. The center of the resulting concentric fringes mark the position of the active quantum Coulomb island. Tuning the magnetic field, we were able to unveil a continuous evolution of active quantum Coulomb islands. This allows to decrypt the complexity of high-magnetic field magnetoresistance oscillations, and opens the way to further local-scale manipulations of QH localized states. CONTACTS vincent.bayot@uclouvain.be serge.huant@grenoble.cnrs.fr herve.courtois@grenoble.cnrs.fr FURTHER READING M. G. Pala et al., Nanotechnology, 20, 264021 (2009) B. Hackens et al., Nature Communications 1:39 (2010). 12
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Date of publication: May 2011 We wo
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Nanosciences Foundation Activity Re
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Part I: ACHIEVEMENTS & PROSPECTS Th
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THE NANOSCIENCES FOUNDATION AT THE
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OUTSTANDING BENEFITS CATALYZED BY T
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The laureates of the 2010 Chairs of
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‘Mobilité d’Excellence’: a n
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INTEGRATION ON SITE BETWEEN BASIC R
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OVERVIEW Fig.3: LANEF framework. Ba
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The Nanosciences Foundation budget
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The evolution of the funding progra
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OVERVIEW Fig. 6: Total number of vi
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ACKNOWLEDGEMENTS One couldn’t fin
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Part II: SCIENTIFIC REPORT 1 - QUAN
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1 - QUANTUM NANOELECTRONICS Moore
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Core/shell nanowires: conductance C
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2 - NANOMAGNETISM AND SPINTRONICS B
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than 10 8 V/m and to compare this t
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sites. The calculations indicate th
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3 - NANOPHOTONICS The optical prope
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Cavity-feeding : decoherence as a r
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4 - MOLECULAR ELECTRONICS Molecular
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5 - NANOMATERIALS, NANOASSEMBLY AND
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Phase-change memory RTRA Project 20
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6 - NANO- CHARACTERISATION AND NANO
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when compared, for example, to the
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7 - NANO APPROACHES TO LIFE SCIENCE
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Innovative biochips to detect and s
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Implantable brain computer interfac
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8 - NANOMODELING, THEORY & SIMULATI
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Growth, patterning, defects & struc
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9 - TECHNOLOGICAL FACILITIES Create
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CRG: The French Cooperative Researc
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The Numerical Simulation Facility T
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10 - EDUCATION AND SCIENTIFIC ANIMA
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Q-NET: a new European Initial Train
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Thesis Prize Award Ceremonies 2009
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2010 Speaker From Date Title Resear
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Workshop “Super Resolution Optica
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Workshop “Electronic Noise and Re
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Workshop « New trends in Electrica
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List of the Quantum Nanoelectronics
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Hélène LE SUEUR Laboratoire de Ph
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Quantum Nanoelectronics Seminars in
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Invitations to talk at seminars: "
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- Anton ANDREEV (University of Wash
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Cellulose Hybrid block copolymers /
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PART 3 S. J. C. Yates, J. J. A. Bas
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D. A. Stewart, I. Savic, and N. Min
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DISPOGRAPH / RTRA project Post-doct
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2009 Call for Proposals MUSCADE Cha
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Piotr Laczkowski, Danny Hykel, Serg
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Part IV: SUPPLEMENTS Appendix 1: th
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Appendix 2: the Foundation’s boar
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Appendix 4: the Steering Committee
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RTRA projects support Major topic A
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Appendix 6: 2010 Call for Proposals
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Page 178 and 179: Roland HERINO (past Director) Jean-
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