Compressibility measurement of the thermal MI--BG transition in an optical lattice

TL;DR

This paper investigates the transition from a Mott insulator to a Bose glass in an ultracold lattice gas by measuring how compressibility varies with disorder, revealing the critical disorder strength for this quantum phase change.

Contribution

It provides the first direct measurement of the MI-BG transition in an optical lattice through core compressibility, highlighting the disorder dependence of compressibility in these phases.

Findings

Identified the disorder threshold for MI to BG transition.

Measured how double occupancy varies with atom number.

Demonstrated disorder-dependent compressibility behavior.

Abstract

Disorder can be applied to transform conducting to insulating states by localizing individual quantum particles. The interplay between disorder and interactions in many-particle systems leads to a richer tapestry of quantum phase transitions. Here, we report the measurement in an ultracold lattice gas of a disorder-induced transition from a state with small disorder-independent compressibility to a state for which compressibility increases with disorder. At zero temperature this is the transition from a Mott insulator (MI) to a Bose glass (BG), both of which are insulating states. This transformation is observed using measurements of core compressibility. By determining how double occupancy changes with atom number, we identify the threshold disorder strength required to switch from disorder-independent MI-like to disorder-dependent BG-like compressible behavior.