Excitons in the Fractional Quantum Hall Effect

TL;DR

This paper reports experimental evidence of exotic fractional excitons in bilayer systems under fractional quantum Hall conditions, revealing two new quantum phases and challenging traditional exciton models.

Contribution

It provides the first experimental signatures of fractional excitons and identifies two novel quantum phases involving unconventional excitonic states.

Findings

Transport signatures of fractional excitons observed

Discovery of a fractional exciton condensate phase

Identification of an exciton involving fermionic and anyonic statistics

Abstract

Excitons, Coulomb-driven bound states of electrons and holes, are typically composed of integer charges. However, in bilayer systems influenced by charge fractionalization, a more exotic form of interlayer exciton can emerge, where pairing occurs between constituents that carry fractional charges. Despite numerous theoretical predictions for such fractional excitons, their experimental observation has remained elusive. Here, we report transport signatures of excitonic pairing within fractional quantum Hall effect states. By probing the composition of these excitons and their impact on the underlying wavefunction, we uncover two novel quantum phases of matter. One of these orders can be viewed as the fractional counterpart of the exciton condensate at a total filling of one, while the other involves a more unusual type of exciton that obeys fermionic and anyonic quantum statistics, challenging the standard paradigm of bosonic excitons.