Interplay of disorder and interaction in the bilayer band-insulator : A Determinant Quantum Monte Carlo study

TL;DR

This study investigates how random on-site disorder affects the phase transition and properties of the bilayer attractive Hubbard model, revealing disorder-induced localization effects and suppression of superfluidity without altering the critical interaction point.

Contribution

It provides the first detailed quantum Monte Carlo analysis of disorder effects on the BI to SF transition in the bilayer attractive Hubbard model.

Findings

Disorder localizes on-site pairs and reduces effective hopping.

Pair-pair correlations are suppressed at finite disorder.

Superfluid phase shrinks with increasing disorder, with a critical disorder strength of about 1.44.

Abstract

Earlier work [arXiv:1206.2407,arXiv:2206.06085] have shown the band insulator (BI) to superfluid (SF) phase transition in the half-filled bilayer attractive Hubbard model. In this paper we append the effects of random on-site disorder on the single particle properties and two particle pair-pair correlations in that model. Using the determinant quantum Monte Carlo simulation we observe that the on-site random disorder plays a significant role in the localization of on-site pairs, hence in the reduction of the effective hopping. This results in an increase of the double occupancy, which is an effect similiar to the attractive interaction. We find no change in the critical value of the interaction at which the model undergoes from BI to SF regime even though the pair-pair correlations get suppressed for finite on-site disorder strengths V_d/t=0.1-0.8. We also confirm that the weak disorder suppresses the SF phase largely in the strong-coupling limit. Hence the region of the SF phase reduces in the presence of random on-site disorder. Finally, through finite-size scaling we have estimated the critical disorder strength V_d^c/t~1.44 at |U|/t=5.