Bilayer Haldane model: From trivial band insulator to fractionalized quantum anomalous Hall insulator

TL;DR

This paper explores a bilayer Haldane model where interactions induce a transition from a trivial insulator to a fractionalized quantum anomalous Hall phase featuring coexisting topological and spin liquid states.

Contribution

It introduces a novel bilayer Haldane model with opposite signs of time-reversal breaking and demonstrates a layer-selective Mott transition leading to a fractionalized QAH insulator.

Findings

Identification of a layer-selective Mott transition

Emergence of a fractionalized QAH insulator with coexisting phases

Analysis of edge electron spectral function near the QAH* phase

Abstract

Motivated by work on the bulk topological proximity effect and the topological bootstrap, we consider two coupled layers of quantum anomalous Hall (QAH) insulators with opposite signs of time-reversal breaking, which leads to a trivial band insulator at half-filling. We study the impact of interactions in this model within slave rotor theory, which leads to a layer-selective Mott transition, resulting in a fractionalized quantum anomalous Hall insulator QAH$^*$ where a Chern band insulator coexists with a chiral spin liquid. We also compute the edge electron spectral function in the vicinity of the QAH$^*$ phase.