Composite fermion dynamics in half-filled Landau levels of graphene

TL;DR

This study uses exact-diagonalization to explore composite fermion behavior in graphene's half-filled Landau levels, revealing stability of the polarized Fermi sea and spontaneous depolarization, implying no Pfaffian phase exists in this system.

Contribution

It provides the first detailed analysis of composite fermion dynamics in graphene's Landau levels, considering pseudospin degeneracy and stability against pairing.

Findings

Polarized Fermi sea remains stable in lowest Landau levels.

Spontaneous depolarization occurs due to lack of pseudospin splitting.

Absence of Pfaffian phase in graphene's half-filled Landau levels.

Abstract

We report on exact-diagonalization studies of correlated many-electron states in the half-filled Landau levels of graphene, including pseudospin (valley) degeneracy. We demonstrate that the polarized Fermi sea of non-interacting composite fermions remains stable against a pairing transition in the lowest two Landau levels. However, it undergoes spontaneous depolarization, which is unprotected owing to the lack of single-particle pseudospin splitting. These results suggest the absence of the Pfaffian phase in graphene.