Mean-field description of pairing effects, BKT physics, and superfluidity in 2D Bose gases

Abstract

We derive a mean-field description for two-dimensional (2D) interacting Bose gases at arbitrary temperatures. We find that genuine Bose-Einstein condensation with long-range coherence only survives at zero temperature. At finite temperatures, many-body pairing effects included in our mean-field theory introduce a finite amplitude for the pairing density, which results in a finite superfluid density. We incorporate Berenzinskii-Kosterlitz-Thouless (BKT) physics into our model by considering the phase fluctuations of our pairing field. This then leads to the result that the superfluid phase is only stable below the BKT temperature due to these phase fluctuations. In the weakly interacting regime at low temperature we compare our theory to previous results from perturbative calculations, renormalization group calculations as well as Monte Carlo simulations. We present a finite-temperature phase diagram of 2D Bose gases. One signature of the finite amplitude of the pairing density field is a two-peak structure in the single-particle spectral function, resembling that of the pseudogap phase in 2D attractive Fermi gases.

9 pages, 3 figures

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Cited by in corpus (9)

• Zero-point energy of ultracold atoms
• Finite-temperature quantum fluctuations in two-dimensional Fermi superfluids
• BCS-BEC crossover of atomic Fermi superfluid in a spherical bubble trap
• 2D dilute Bose mixture at low temperatures
• Addressing energy density functionals in the language of path-integrals I: Comparative study of diagrammatic techniques applied to the (0+0)-D $O(N)$-symmetric ${\phi }^4$-theory
• Ground-state properties of a dilute two-dimensional Bose gas
• Addressing energy density functionals in the language of path-integrals II: Comparative study of functional renormalization group techniques applied to the (0+0)-D $O(N)$-symmetric ${\phi }^4$-theory
• Flow-based Nonperturbative Simulation of First-order Phase Transitions
• Critical temperature of trapped interacting bosons from large-N based theories