Mean-field phase diagram of disordered bosons in a lattice at non-zero temperature

TL;DR

This paper presents a mean-field analysis of disordered bosons in a lattice at non-zero temperature, identifying phase boundaries and showing temperature effects on phase transitions.

Contribution

It introduces criteria based on superfluid density and low-energy excitations to distinguish phases, and maps the phase diagram considering finite temperature effects.

Findings

Temperature causes a significant shift in the Bose glass-superfluid boundary.

Compressibility is not a reliable phase criterion at non-zero temperature.

Phase diagram reveals the impact of disorder and temperature on phase stability.

Abstract

Bosons in a periodic lattice with on-site disorder at low but non-zero temperature are considered within a mean-field theory. The criteria used for the definition of the superfluid, Mott insulator and Bose glass are analysed. Since the compressibility does never vanish at non-zero temperature, it can not be used as a general criterium. We show that the phases are unambiguously distinguished by the superfluid density and the density of states of the low-energy exitations. The phase diagram of the system is calculated. It is shown that even a tiny temperature leads to a significant shift of the boundary between the Bose glass and superfluid.