Evidence for a topological "exciton Fermi sea" in bilayer graphene

TL;DR

This paper provides theoretical and numerical evidence for a novel phase in bilayer graphene, where a Fermi sea of topological excitons emerges due to Landau level crossings, enriching the understanding of quantum Hall physics.

Contribution

It introduces the concept of a topological exciton Fermi sea in bilayer graphene, supported by theoretical models and numerical simulations, advancing the study of fractional quantum Hall states.

Findings

Observation of a coexistence of even-denominator Hall plateau with inter-layer excitons

Identification of a new phase: a Fermi sea of topological excitons

Numerical evidence supporting the existence of this exotic phase

Abstract

The quantum Hall physics of bilayer graphene is extremely rich due to the interplay between a layer degree of freedom and delicate fractional states. Recent experiments show that when an electric field perpendicular to the bilayer causes Landau levels of opposing layers to cross in energy, a even-denominator Hall plateau can coexist with a finite density of inter-layer excitons. We present theoretical and numerical evidence that this observation is due to a new phase of matter -- a Fermi sea of topological excitons.