A disordered insulator in an optical lattice

Abstract

Disorder can profoundly affect the transport properties of a wide range of quantum materials. At present, significant disagreement exists regarding features of the disordered Bose–Hubbard model, which is used to study disorder in strongly correlated bosonic systems1,2. Here, by measuring transport3 in a disordered optical lattice4, we discover a disorder-induced superfluid-to-insulator transition in this system, in quantitative agreement with a predicted superfluid–Bose-glass transition from recent numerical simulations5. Both the superfluid-to-insulator transition and correlated changes in the atomic quasimomentum distribution—which verify a simple model for the interplay of disorder and interactions in this system—are phenomena new to the unit-filling regime explored in this work. We find that increasing disorder strength generically leads to greater dissipation, excluding predictions of a disorder-induced or ‘re-entrant’ superfluid. Whereas the absence of a re-entrant superfluid may be explained by finite temperature, the measured bounds on entropy strongly constrain theory.