Mean field theory of superglasses

TL;DR

This paper develops a mean field theory for superglasses, revealing three distinct phases and the nature of their transitions, with implications for disordered bosonic systems like supersolids and helium in porous media.

Contribution

It introduces a mean field model capturing superfluid, glassy, and coexistence phases in disordered bosonic systems, analyzing phase transitions and properties of the superglass phase.

Findings

Identification of three low-temperature phases and their phase transitions.

Superfluidity is suppressed at T=0 due to glassy correlations.

The superglass phase exhibits anticorrelations and nonmonotonous superfluid order parameter.

Abstract

We study the interplay of superfluidity and glassy ordering of hard core bosons with random, frustrating interactions. This is motivated by bosonic systems such as amorphous supersolid, disordered superconductors with preformed pairs, and helium in porous media. We analyze the fully connected mean field version of this problem, which exhibits three low-temperature phases, separated by two continuous phase transitions: an insulating, glassy phase with an amorphous frozen density pattern, a nonglassy superfluid phase, and an intermediate phase, in which both types of order coexist. We elucidate the nature of the phase transitions, highlighting in particular the role of glassy correlations across the superfluid-insulator transition. The latter suppress superfluidity down to T=0, due to the depletion of the low-energy density of states, unlike in the standard BCS scenario. Further, we investigate the properties of the coexistence (superglass) phase. We find anticorrelations between the local order parameters and a nonmonotonous superfluid order parameter as a function of T. The latter arises due to the weakening of the glassy correlation gap with increasing temperature. Implications of the mean field phenomenology for finite dimensional bosonic glasses with frustrating Coulomb interactions are discussed.