How localized bosons manage to become superfluid

TL;DR

This paper investigates the superfluid-to-Bose glass transition in a disordered Bose-Hubbard model using a simple variational wavefunction, identifying the transition through superfluid stiffness, overlap matrix criteria, and entanglement entropy.

Contribution

Introduces a simple variational wavefunction approach to study the transition, and compares multiple criteria for identifying the superfluid-to-Bose glass transition.

Findings

Superfluid stiffness effectively signals the transition.

Overlap matrix criterion agrees with superfluid stiffness.

Entanglement entropy serves as a good transition estimator.

Abstract

We study the superfluid-to-Bose glass transition in a disordered Bose-Hubbard model through a very simple variational wavefunction: a permanent of non-orthogonal single-particle wavefunctions that are variationally determined. The transition is identified by the behavior of the superfluid stiffness. We also introduce a less rigorous but very enlightening criterium for the transition, which is related to the overlap matrix among the single-particle wavefunctions that are used to built the permanent. We find that the two criteria agree quite well. We finally consider a further quantity, the bipartite entanglement entropy, which also provides a good estimator for the superfluid-to-Bose glass transition.