SU(4) composite fermions in graphene: New fractional quantum Hall states

TL;DR

This paper predicts new fractional quantum Hall states in graphene arising from SU(4) symmetry, involving spin and valley degeneracies, which differ from known states in GaAs and depend on specific fractional fillings.

Contribution

The study introduces novel FQHE states in graphene with SU(4) symmetry, expanding understanding beyond previously known states and detailing their structure and conditions for observation.

Findings

Prediction of new SU(4) FQHE states at specific fractions

Conditions for observing these states and phase transitions

Description of the states' structure and excitations

Abstract

Theoretical studies of the fractional quantum Hall effect (FQHE) in graphene have so far focused on the plausibility and stability of the previously known FQHE states for the interaction matrix elements appropriate for graphene. We consider FQHE for SU(4) symmetry, as appropriate for the situation when all four spin and valley Landau bands are degenerate, and predict new FQHE states that have no analog in GaAs. These result from an essential interplay between the two-fold spin and valley degeneracies at fractions of the form $\nu=n/(2pn\pm 1)$, for $n\geq 3$. Conditions are outlined for the observation of these states and quantum phase transitions between them; the structure of these states and their excitations is also described.