Finite temperature coherence of the ideal Bose gas in an optical lattice

Abstract

In current experiments with cold quantum gases in periodic potentials, interference fringe contrast is typically the easiest signal in which to look for effects of non-trivial many-body dynamics. In order better to calibrate such measurements, we analyse the background effect of thermal decoherence as it occurs in the absence of dynamical interparticle interactions. We study the effect of optical lattice potentials, as experimentally applied, on the condensed fraction of a non-interacting Bose gas in local thermal equilibrium at finite temperatures. We show that the experimentally observed decrease of the condensate fraction in the presence of the lattice can be attributed, up to a threshold lattice height, purely to ideal gas thermodynamics; conversely we confirm that sharper decreases in first-order coherence observed in stronger lattices are indeed attributable to many-body physics. Our results also suggest that the fringe visibility 'kinks' observed in F.Gerbier et al., Phys. Rev. Lett. 95, 050404 (2005) may be explained in terms of the competition between increasing lattice strength and increasing mean gas density, as the gaussian profile of the red-detuned lattice lasers also increases the effective strength of the harmonic trap.

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• Cold bosonic atoms in optical lattices
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• Adiabatic cooling of Fermions in an optical lattice
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• Bose-Einstein condensation in an optical lattice
• The role of interactions, tunneling and harmonic confinement on the adiabatic loading of bosons in an optical lattice
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Cited by in corpus (5)

• Suppression of the critical temperature for superfluidity near the Mott transition: validating a quantum simulator
• Critical temperature of a Bose gas in an optical lattice
• Dimensional crossover of a boson gas in multilayers
• Two-step condensation of lattice bosons
• Global and local condensate and superfluid fraction of a few hard core bosons in a cubic optical lattice plus external harmonic confinement