Fractional Quantum Hall Effect of Hard-Core Bosons in Topological Flat Bands

TL;DR

This paper demonstrates the emergence of fractional quantum Hall states in topological flat band models with hard-core bosons, revealing robust gaps and phase transitions without Landau levels.

Contribution

It provides the first detailed study of FQHE in TFB models with hard-core bosons, including phase diagrams and transition analysis.

Findings

FQHE states show even degeneracy on a torus

Robust spectral gaps separate FQHE states from excitations

Quantum phase diagrams reveal transitions to symmetry-breaking phases

Abstract

Recent proposals of topological flat band (TFB) models have provided a new route to realize the fractional quantum Hall effect (FQHE) without Landau levels. We study hard-core bosons with short-range interactions in two representative TFB models, one of which is the well known Haldane model (but with different parameters). We demonstrate that FQHE states emerge with signatures of even number of quasi-degenerate ground states on a torus and a robust spectrum gap separating these states from higher energy spectrum. We also establish quantum phase diagrams for the filling factor 1/2 and illustrate quantum phase transitions to other competing symmetry-breaking phases.