Reentrant phase transitions involving glassy and superfluid orders in the random hopping Bose–Hubbard model

Abstract

We study a system of strongly correlated bosons with off-diagonal disorder, i.e., randomness in the kinetic energy, and find a family of reentrant phase transitions that occur as a function of the on-site interaction. We model the system using the paradigmatic Bose–Hubbard Hamiltonian with a random hopping term and solve it employing the replica trick and Trotter–Suzuki expansion known from quantum spin-glasses. From subsequent numerical calculations, we find three distinct phase boundaries at which the reentrant transitions occur: between glass and disordered phase, between superglass and superfluid ones, and between superfluid and disordered phases. All three happen at temperatures slightly above critical temperatures of corresponding non-interacting systems. When the emerging and disappearing order is glassy, this corresponds to the interplay of the thermal energy and the spread of hoppings. When superfluidity is involved, thermal fluctuations must slightly overcome the mean hopping in turn for the reentrance to occur.