Properties of the Superfluid in the Disordered Bose-Hubbard Model

TL;DR

This study uses Quantum Monte-Carlo simulations to analyze the superfluid phase in the three-dimensional disordered Bose-Hubbard model, revealing how disorder shape influences phase behavior and demonstrating self-averaging properties relevant to ultracold atomic gas experiments.

Contribution

It provides a detailed analysis of disorder effects on superfluid properties and phase boundaries in the disordered Bose-Hubbard model, highlighting the role of disorder shape and finite-size effects.

Findings

Superfluid fraction and compressibility are self-averaging.

Qualitative similarities in phase behavior across disorder types.

Finite-size effects are significant near phase boundaries.

Abstract

We investigate the properties of the superfluid phase in the three-dimensional disordered Bose-Hubbard model using Quantum Monte-Carlo simulations. The phase diagram is generated using Gaussian disorder on the on-site potential. Comparisons with box and speckle disorder show qualitative similarities leading to the re-entrant behavior of the superfluid. Quantitative differences that arise are controlled by the specific shape of the disorder. Statistics pertaining to disorder distributions are studied for a range of interaction strengths and system sizes, where strong finite-size effects are observed. Despite this, both the superfluid fraction and compressibility remain self-averaging throughout the superfluid phase. Close to the superfluid-Bose-glass phase boundary, finite-size effects dominate but still suggest that self-averaging holds. Our results are pertinent to experiments with ultracold atomic gases where a systematic disorder averaging procedure is typically not possible.