Phase correlations and quasicondensate in a two-dimensional ultracold Fermi gas

摘要

The interplay between dimensionality, coherence and interaction in superfluidFermi gases is analyzed by the phase correlation function of the field offermionic pairs. We calculate this phase correlation function for atwo-dimensional superfluid Fermi gas with $s$-wave interactions within theGaussian pair fluctuation formalism. The spatial behavior of the correlationfunction is shown to exhibit a rapid (exponential) decay at short distances anda characteristic algebraic decay at large distances, with an exponent matchingthat expected from Berezinskii-Kosterlitz-Thouless theory of 2D Bosesuperfluids. We conclude that the Gaussian pair fluctuation approximation isable to capture the physics of quasi long-range order in two-dimensional Fermigases.