Universal correlations and coherence in quasi-two-dimensional trapped Bose gases

Understand

We study the quasi-two-dimensional Bose gas in harmonic traps at temperatures above the Kosterlitz-Thouless transition, where the gas is in the normal phase.

• We show that mean-field theory takes into account the dominant interaction effects for experimentally relevant trap geometries.
• Comparing with Quantum Monte Carlo calculations, we quantify the onset of the fluctuation regime, where correlations beyond mean-field become important.
• Although the density profile depends on the microscopic parameters of the system, we show that the correlation density (the difference between the exact and the mean-field density) is accurately described by a universal expression, obtained from classical-field calculations of the homogeneous strictly two-dimensional gas.