Finite-temperature properties of quasi-2D Bose-Einstein condensates

TL;DR

This study uses path integral Monte Carlo simulations to explore how temperature and interactions influence the properties of dilute quasi-2D Bose gases, revealing unique superfluid behavior and transition temperatures compared to other geometries.

Contribution

The paper provides detailed finite-temperature analysis of quasi-2D Bose-Einstein condensates, highlighting the effects of interactions on superfluidity and dimensional crossover, with comparisons to semi-classical and ideal models.

Findings

Superfluid fraction decreases faster in quasi-2D than in quasi-1D or 3D systems with temperature.

The minimum aspect ratio for quasi-2D behavior increases with interaction strength.

Kosterlitz-Thouless transition temperature decreases as interaction strength increases.

Abstract

Using the finite-temperature path integral Monte Carlo method, we investigate dilute, trapped Bose gases in a quasi-two dimensional geometry. The quantum particles have short-range, s-wave interactions described by a hard-sphere potential whose core radius equals its corresponding scattering length. The effect of both the temperature and the interparticle interaction on the equilibrium properties such as the total energy, the density profile, and the superfluid fraction is discussed. We compare our accurate results with both the semi-classical approximation and the exact results of an ideal Bose gas. Our results show that for repulsive interactions, (i) the minimum value of the aspect ratio, where the system starts to behave quasi-two dimensionally, increases as the two-body interaction strength increases, (ii) the superfluid fraction for a quasi-2D Bose gas is distinctly different from that for both a quasi-1D Bose gas and a true 3D system, i.e., the superfluid fraction for a quasi-2D Bose gas decreases faster than that for a quasi-1D system and a true 3D system with increasing temperature, and shows a stronger dependence on the interaction strength, (iii) the superfluid fraction for a quasi-2D Bose gas lies well below the values calculated from the semi-classical approximation, and (iv) the Kosterlitz-Thouless transition temperature decreases as the strength of the interaction increases.