Quantum glass phases in the disordered Bose-Hubbard model

TL;DR

This paper uses Quantum Monte Carlo simulations to map the phase diagram of the disordered Bose-Hubbard model, revealing novel quantum glass phases including a Mott glass that is incompressible yet gapless.

Contribution

It introduces the discovery of a Mott glass phase and characterizes multiple quantum glass phases in the disordered Bose-Hubbard model.

Findings

Identification of a Mott glass phase that is incompressible and gapless

Observation of quantum glass phases intervening between Mott insulator and superfluid

Numerical evidence from global and local observables supporting phase properties

Abstract

The phase diagram of the Bose-Hubbard model in the presence of off-diagonal disorder is determined using Quantum Monte Carlo simulations. A sequence of quantum glass phases intervene at the interface between the Mott insulating and the Superfluid phases of the clean system. In addition to the standard Bose glass phase, the coexistence of gapless and gapped regions close to the Mott insulating phase leads to a novel Mott glass regime which is incompressible yet gapless. Numerical evidence for the properties of these phases is given in terms of global (compressibility, superfluid stiffness) and local (compressibility, momentum distribution) observables.