Superfluid Bose gas in two dimensions

Abstract

We investigate Bose-Einstein condensation for ultracold bosonic atoms in two-dimensional systems. The functional renormalization group for the average action allows us to follow the effective interactions from molecular scales (microphysics) to the characteristic extension of the probe $l$ (macrophysics). In two dimensions the scale dependence of the dimensionless interaction strength $\lambda$ is logarithmic. Furthermore, for large $l$ the frequency dependence of the inverse propagator becomes quadratic. We find an upper bound for $\lambda$, and for large $\lambda$ substantial deviations from the Bogoliubov results for the condensate depletion, the dispersion relation and the sound velocity. The melting of the condensate above the critical temperature $T_c$ is associated to a phase transition of the Kosterlitz-Thouless type. The critical temperature in units of the density, $T_c/n$, vanishes for $l\to \infty$ logarithmically.

10 pages, 12 figures, reference added

References in corpus (5)

• Many-Body Physics with Ultracold Gases
• Interference of an array of independent Bose-Einstein condensates
• Two-dimensional Bose-Einstein condensate in an optical surface trap
• Functional renormalization for Bose-Einstein Condensation
• Competing orders in thermally fluctuating superconductors in two dimensions

Cited by in corpus (1)

• Infrared behavior and spectral function of a Bose superfluid at zero temperature