Dipole representation of composite fermions in graphene quantum Hall systems

TL;DR

This study extends the dipole representation of composite fermions to graphene's quantum Hall systems, analyzing pairing instabilities at half-filled Landau levels and finding the regularized state more energetically favorable without pairing.

Contribution

It adapts the dipole representation framework to graphene's quantum Hall context, incorporating particle-hole symmetry and analyzing the energetic stability of paired states.

Findings

No well-defined pairing instabilities found in the dipole representation.

Regularized, boost-invariant state is energetically more favorable.

Results align with experimental and numerical studies.

Abstract

The even denominator fractional quantum Hall effect has been experimentally observed in graphene in the fourth Landau level ($n = 3$). This paper is motivated by recent studies regarding the possibility of pairing and the nature of the ground state in this system. By extending the dipole representation of composite fermions, we adapt this framework to the context of graphene's quantum Hall systems, with a focus on half-filled Landau levels. We derive an effective Hamiltonian that incorporates the key symmetry of half-filled Landau levels, particularly particle-hole symmetry. At the Fermi level, the energetic instability of the dipole state is influenced by the interplay between topology and symmetry, driving the system towards a critical state. We explore the possibility that this critical state stabilizes into one of the paired states with well-defined pairing solutions. However, our results demonstrate that the regularized state which satisfies boost invariance at Fermi level and lacks well-defined pairing instabilities emerges as energetically more favorable. Therefore, we find no well-defined pairing instabilities of composite fermions in the dipole representation in the half-filled fourth Landau level ($ n = 3 $) of electrons in graphene. Although the theory of composite fermions has its limitations, further research is required to investigate other possible configurations. We discuss the consistency of our results with experimental and numerical studies, and their relevance for future research efforts.