A Gaussian Theory of Superfluid--Bose-Glass Phase Transition

TL;DR

This paper demonstrates that infinitesimal gaussian quantum fluctuations can destroy superfluidity in disordered boson systems in 1D and 2D, establishing a finite critical disorder threshold regardless of particle repulsion.

Contribution

It introduces a gaussian approximation framework to analyze the superfluid--Bose-glass transition, revealing universal critical exponents and excitation properties.

Findings

Gaussian fluctuations destroy superfluidity at finite disorder in 1D and 2D.

Critical exponent ratio is universal across systems.

Density of states and mobility edge are characterized at transition.

Abstract

We show that gaussian quantum fluctuations, even if infinitesimal, are sufficient to destroy the superfluidity of a disordered boson system in 1D and 2D. The critical disorder is thus finite no matter how small the repulsion is between particles. Within the gaussian approximation, we study the nature of the elementary excitations, including their density of states and mobility edge transition. We give the gaussian exponent $\eta$ at criticality in 1D and show that its ratio to $\eta$ of the pure system is universal.