Quantum Monte Carlo study of a one-dimensional phase-fluctuating condensate

TL;DR

This study numerically investigates a one-dimensional Bose gas in an optical lattice, identifying a quasicondensate regime characterized by negligible density fluctuations but significant phase fluctuations, and explores quantum depletion effects.

Contribution

It provides a detailed numerical analysis of phase fluctuations in 1D Bose gases, extending beyond mean-field approximations to reveal new phase-correlation behaviors.

Findings

Identification of a temperature regime with phase fluctuations but negligible density fluctuations

Agreement with mean-field results in the weakly interacting limit

Different phase-correlation properties beyond mean-field regimes

Abstract

We study numerically the low temperature behavior of a one-dimensional Bose gas trapped in an optical lattice. For a sufficient number of particles and weak repulsive interactions, we find a clear regime of temperatures where density fluctuations are negligible but phase fluctuations are considerable, i.e., a quasicondensate. In the weakly interacting limit, our results are in very good agreement with those obtained using a mean-field approximation. In coupling regimes beyond the validity of mean-field approaches, a phase-fluctuating condensate also appears, but the phase-correlation properties are qualitatively different. It is shown that quantum depletion plays an important role.