Interlayer phase coherence and composite fermions

TL;DR

This paper explores the role of interlayer phase coherence and the extension of the composite fermion concept in bilayer quantum Hall systems, highlighting new FQHE states observed in graphene and the potential for CF interlayer coherence.

Contribution

It extends the composite fermion framework to bilayer systems and discusses the possibility of interlayer phase coherence of CFs, explaining recent experimental findings in graphene.

Findings

Identification of FQHE states unique to bilayer systems

Proposal of CF interlayer phase coherence in bilayer quantum Hall states

Discussion of experimental observations in graphene double layers

Abstract

The fractional quantum Hall effect (FQHE) realized in two-dimensional electron systems is explained by the emergent composite fermions (CF) out of ordinary electrons. It is possible to write down explicit wavefunctions explaining many if not all FQHE states. In bilayer systems there is a regime at integer filling of the lowest Landau level that displays a spontaneous breakdown of the U(1) relative phase between the two layers. This can be seen as interlayer phase coherence (ILC) in terms of electrons. Recent experiments in double layer samples of graphene have revealed the appearance of many FQHE states unique to the bilayer case. We discuss extensions of the CF idea in this situation as well as the possible existence of ILC of CFs.