Kosterlitz-Thouless transition of the quasi two-dimensional trapped Bose gas

TL;DR

This paper uses Quantum Monte Carlo simulations to study the Kosterlitz-Thouless transition in a large, quasi-two-dimensional trapped Bose gas, providing insights into experimental signatures and finite-size effects.

Contribution

It presents large-scale Quantum Monte Carlo calculations of the transition in a quasi-2D Bose gas, linking theoretical predictions with experimental observations.

Findings

Identification of the transition temperature T_KT via density and moment of inertia.

Observation of a large condensate fraction in small systems that diminishes with size.

Application of local-density approximation to interpret results.

Abstract

We present Quantum Monte Carlo calculations with up to N=576000 interacting bosons in a quasi two-dimensional trap geometry closely related to recent experiments with atomic gases. The density profile of the gas and the non-classical moment of inertia yield intrinsic signatures for the Kosterlitz--Thouless transition temperature T_KT. From the reduced one-body density matrix, we compute the condensate fraction, which is quite large for small systems. It decreases slowly with increasing system sizes, vanishing in the thermodynamic limit. We interpret our data in the framework of the local-density approximation, and point out the relevance of our results for the analysis of experiments.