Scientific Report - BEC

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Nonlinear dynamics and solitons 44[13] A.J. Leggett in Modern Trends in the Theory of Condensed Matter, editedbyA.Pekalski and R. Przystawa (Springer-Verlag, Berlin, 1980); M. Randeria in BoseEinstein Condensation, edited by A. Griffin, D. Snoke, and S. Stringari (Cambridge,Cambridge, England, 1995).[14] R. Sensarma, M. Randeria, T.-L. Ho, Phys. Rev. Lett. 96, 090403 (2006).
Ultracold gases in optical lattices 45ULTRACOLD GASES IN OPTICAL LATTICESDynamical instability and dispersion management of an attractive condensateThe properties of Bose-Einstein condensates propagating in optical lattices have beenthe object of an intense experimental and theoretical activity in recent years [1]. Thesestudies have been mainly focused on the case of repulsive interactions. Since BECswith tunable attractive interactions are becoming available in current experiments [2],this opens now interesting perspectives for the investigations of the behaviour of BECsin optical lattices in unexplored regimes.Motivated by this, we have investigated the properties of an attractive BEC movingin a 1D optical lattice [3], finding a remarkable behaviour compared to the case ofrepulsive interactions investigated so far. There are at least three points that makethe attractive case particularly interesting. i) Increasing the lattice velocity stabilizesthe system: attractive condensates are dynamically unstable at low quasimomenta, butcan be stabilized above a certain critical velocity (see Fig. 1). This is just the oppositebehaviour of that found for repulsive BECs [4, 5], and can be naively explained withthe fact that changing the sign of interactions is equivalent to a change of sign in theeffective mass. ii) For low quasimomenta and shallow lattices DI takes place via longwavelength excitations. In this regime the excitation modes are not sufficient to producea site-to-site dephasing, but are rather expected to induce collective oscillation of thesystem, producing density modulations that extend over several sites of the lattice. iii)Negative effective mass and DI appear in separate regimes, thus opening the possibilityfor being investigated in a more clear way.These effects have been discussed by comparing the predictions of the Bogoliubovlinear stability analysis with the solution of a time dependent Gross-Pitaevskii modelfor the waveguide expansion of the condensate in the presence of a moving lattice [3].We have shown that in the unstable regime breathing-like oscillations are producedfor low velocities, and that the absence of dynamical instability for higher velocitiesallows for the control of condensate dispersion when the effective mass is switched frompositive to negative values [6, 7].BECs in quasiperiodic latticesOne of the most intriguing phenomena in physics is the localization of waves in disorderedmedia, originally predicted by P. W. Anderson fifty years ago, in the context
Page 1 and 2: Istituto Nazionale per la Fisica de
Page 3 and 4: ContentsOverview 5The scientific mi
Page 5 and 6: OverviewThe scientific missionThe I
Page 7 and 8: The BEC Center 7links between theor
Page 9 and 10: OrganizationManagementDirector* San
Page 11 and 12: Research staff 11Graduate Students*
Page 13 and 14: ResearchThis report provides an ove
Page 15 and 16: Fermionic superfluidity and BCS-BEC
Page 17 and 18: Fermionic superfluidity and BCS-BEC
Page 19 and 20: Polarized Fermi gases 19Figure 1: D
Page 21 and 22: Polarized Fermi gases 21showing tha
Page 23 and 24: Quantum Monte Carlo methods 23QUANT
Page 25 and 26: Quantum Monte Carlo methods 25Figur
Page 27 and 28: Quantum Monte Carlo methods 27Figur
Page 29 and 30: Quantum Monte Carlo methods 291.081
Page 31 and 32: Quantum Monte Carlo methods 31The n
Page 33 and 34: Rotating quantum gases 33ROTATING Q
Page 35 and 36: Rotating quantum gases 350.175(b)2.
Page 37 and 38: Rotating quantum gases 37Figure 3:
Page 39 and 40: Nonlinear dynamics and solitons 39N
Page 41 and 42: Nonlinear dynamics and solitons 41F
Page 43: Nonlinear dynamics and solitons 43u
Page 47 and 48: Ultracold gases in optical lattices
Page 53 and 54: Dipolar gases 53panding cloud both
Page 55 and 56: Dipolar gases 558765μ/U NN4321(a)M
Page 57 and 58: Dipolar gases 57modifies the vortex
Page 59 and 60: Semiconductor microcavities and exc
Page 67 and 68: Quantum Optics and Quantum Fields 6
Page 73 and 74: Casimir forces 73000000000000000000
Page 75 and 76: Casimir forces 7543Environm entTem
Page 77 and 78: Casimir forces 77where P 0 (l) isth
Page 79 and 80: Matter-waves interferometry 79MATTE
Page 81 and 82: Matter-waves interferometry 81where
Page 83 and 84: Matter-waves interferometry 83Figur
Page 85 and 86: Matter-waves interferometry 85p Δ
Page 87 and 88: Matter-waves interferometry 87phase
Page 89 and 90: Matter-waves interferometry 89evolv
Page 91 and 92: Matter-waves interferometry 91parti
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Quantum information processing 95Fi
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Quantum information processing 97In
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Quantum information processing 99[7
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Projects and scientific collaborati
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Publications 107PublicationsThe fol
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Publications 109and M. Inguscio, Na
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Publications 111Quantum Monte Carlo
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Publications 113Parametric oscillat
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Publications 115Healing length and
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Publications 117Diffused vorticity
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Talks at workshops and conferences
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Visitors 131Michal Kolar (Palacky U
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Events and outreachConferences orga
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Events and outreach 135Resonant spi
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Events and outreach 137Superfluidit
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Events and outreach 139Francesco Ne
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Events and outreach 141Two- and thr
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Events and outreach 143Surface-atom
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