Quench Spectroscopy of a Disordered Quantum System

TL;DR

This paper demonstrates that quench spectroscopy can effectively characterize spectral properties and phase transitions in disordered quantum systems, providing a versatile tool for experimental and theoretical studies.

Contribution

It introduces quench spectroscopy as a method to fully characterize disordered phases and distinguish between superfluid, Bose glass, and Mott insulator phases.

Findings

Identifies gapless excitations in the Bose-Hubbard model.

Locates the Mott insulator to Bose glass transition.

Distinguishes phases using spectral and spatially-resolved spectroscopy.

Abstract

The characterization of excitations in disordered quantum systems is a central issue in connection with glass physics and many-body localization. Here, we show that quench spectroscopy of a disordered model, as realized from its out-of-equilibrium dynamics following a global quench, allows us to fully characterize the spectral properties of the disordered phases. In the Bose-Hubbard model, a clear signature of gapless excitations in momentum-resolved spectroscopy enables us to accurately locate the Mott insulator to Bose glass transition, while the presence or absence of a well-defined soundlike mode distinguishes the superfluid from the Bose glass phase. Moreover, spatially-resolved spectroscopy provides local spectral properties and allows us to extract the typical spacing of gapless regions, giving a second independent way to uniquely identify all three phases. Our findings have far-ranging implications for a variety of experimental platforms, and offer a powerful and versatile probe of the low-energy phases of disordered systems.