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Title: Superfluid Fermi Gas in a 1D Optical Lattice

Abstract

We calculate the superfluid transition temperature for a two-component 3D Fermi gas in a 1D tight optical lattice and discuss a dimensional crossover from the 3D to quasi-2D regime. For the geometry of finite size discs in the 1D lattice, we find that even for a large number of atoms per disc the critical effective tunneling rate for a quantum transition to the Mott insulator state can be large compared to the loss rate caused by three-body recombination. This allows the observation of the Mott transition, in contrast to the case of Bose-condensed gases in the same geometry.

Authors:
 [1];  [2];  [3]
  1. BEC-INFM and Dipartimento di Fisica, Universita di Trento, 1-38050 Povo (Italy)
  2. Laboratoire Physique Theorique et Modeles Statistiques, Universite Paris Sud, Batiment 100, 91405 Orsay Cedex (France)
  3. (Netherlands)
Publication Date:
OSTI Identifier:
20771619
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 26; Other Information: DOI: 10.1103/PhysRevLett.95.260402; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BOSE-EINSTEIN GAS; FERMI GAS; RECOMBINATION; SUPERFLUIDITY; THREE-BODY PROBLEM; TRANSITION TEMPERATURE; TUNNEL EFFECT

Citation Formats

Orso, G., Shlyapnikov, G.V., and Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam. Superfluid Fermi Gas in a 1D Optical Lattice. United States: N. p., 2005. Web. doi:10.1103/PhysRevLett.95.260402.
Orso, G., Shlyapnikov, G.V., & Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam. Superfluid Fermi Gas in a 1D Optical Lattice. United States. doi:10.1103/PhysRevLett.95.260402.
Orso, G., Shlyapnikov, G.V., and Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam. Sat . "Superfluid Fermi Gas in a 1D Optical Lattice". United States. doi:10.1103/PhysRevLett.95.260402.
@article{osti_20771619,
title = {Superfluid Fermi Gas in a 1D Optical Lattice},
author = {Orso, G. and Shlyapnikov, G.V. and Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam},
abstractNote = {We calculate the superfluid transition temperature for a two-component 3D Fermi gas in a 1D tight optical lattice and discuss a dimensional crossover from the 3D to quasi-2D regime. For the geometry of finite size discs in the 1D lattice, we find that even for a large number of atoms per disc the critical effective tunneling rate for a quantum transition to the Mott insulator state can be large compared to the loss rate caused by three-body recombination. This allows the observation of the Mott transition, in contrast to the case of Bose-condensed gases in the same geometry.},
doi = {10.1103/PhysRevLett.95.260402},
journal = {Physical Review Letters},
number = 26,
volume = 95,
place = {United States},
year = {Sat Dec 31 00:00:00 EST 2005},
month = {Sat Dec 31 00:00:00 EST 2005}
}
  • We develop the hydrodynamic theory of Fermi superfluids in the presence of a periodic potential. The relevant parameters governing the propagation of sound (compressibility and effective mass) are calculated in the weakly interacting BCS limit. The conditions of stability of the superfluid motion with respect to creation of elementary excitations are discussed. We also evaluate the frequency of the center-of-mass oscillation when the superfluid gas is additionally confined by a harmonic trap.
  • We study the sound velocity in cubic and noncubic three-dimensional optical lattices. We show how the van Hove singularity of the free Fermi gas is smoothed by interactions and eventually vanishes when interactions are strong enough. For noncubic lattices, we show that the speed of sound (Bogoliubov-Anderson phonon) shows clear signatures of dimensional crossover both in the one- and two-dimensional limits.
  • The nonlinear Landau-Zener tunneling and the nonlinear Rabi oscillations of superfluid Fermi gases between Bloch bands in an accelerating optical lattice are discussed. Within the hydrodynamic theory and a two-level model, the tunneling probability of superfluid Fermi gases between Bloch bands is obtained. We find that, as the system crosses from the Bose-Einstein condensation (BEC) side to the BCS side, the tunneling rate is closely related to the particle density: when the density is smaller (larger) than a critical value, the tunneling rate at unitarity is larger (smaller) than that in the BEC limit. This is well explained in termsmore » of an effective interaction and an effective potential. Furthermore, the nonlinear Rabi oscillations of superfluid Fermi gases between the bands are discussed by imposing a periodic modulation on the level bias and the strength of the lattice. Analytical expressions of the critical density for suppressing or enhancing the Rabi oscillations are obtained. It is shown that, as the system crosses from the BEC side to the BCS side, the critical density strongly depends on the modulation parameters (i.e., the modulation amplitude and the modulation frequency). For a fixed density, a high-frequency or low-frequency modulation can suppress or enhance the Rabi oscillations both at unitarity and in the BEC limit. For an intermediate modulation frequency, the Rabi oscillations are chaotic along the entire BEC-BCS crossover, especially, on the BCS side. Interestingly, we find that the modulation of the lattice strength only with an intermediate modulation frequency has significant effect on the Rabi oscillations both in the BEC limit and at unitarity; that is, an intermediate-frequency modulation can enhance the Rabi oscillations, especially on the BCS side.« less
  • To describe the tunneling dynamics of a stack of two-dimensional fermionic superfluids in an optical potential, we derive an effective action functional from a path integral treatment. This effective action leads in the saddle point approximation to equations of motion for the density and the phase of the superfluid Fermi gas in each layer. In the strong coupling limit (where bosonic molecules are formed) these equations reduce to a discrete nonlinear Schroedinger equation, where the molecular tunneling amplitude is reduced for large binding energies. In the weak coupling (BCS) regime, we study the evolution of the stacked superfluids and derivemore » an approximate analytical expression for the oscillation frequency of the center of mass in an external harmonic potential. In both the weak and intermediate coupling regimes, the detection of the Josephson oscillations described by our path integral formalism constitutes experimental evidence for the fermionic superfluid regime.« less
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