Possibility of magnetic field induced Composite Fermi sea in neutral Graphene

TL;DR

This paper proposes that in neutral graphene under strong magnetic fields, a correlated SU(4) composite Fermi sea may form, challenging the conventional integer quantum Hall state and explaining experimental observations of a gapless state.

Contribution

It introduces the possibility of a composite Fermi sea in neutral graphene driven by correlation energy, offering a new perspective on quantum Hall states in this system.

Findings

Correlation energy favors SU(4) singlet Fermi sea formation.

Destabilization of the ferromagnetic integer quantum Hall state.

Potential for paired Hall states from residual interactions.

Abstract

Neutral graphene in strong magnetic fields is believed to be an (exchange stabilized) integer Hall state of completely filled up spin (say) and empty down spin bands of n = 0, two fold valley degenerate Landau levels. We suggest that correlation energy gain from a nearly SU(4) singlet (2 spin $\times$ 2 valley) composite fermi sea formation, at $\nu \approx$ \hlf filling for each component, destabilizes ferromagnetic integer quantum Hall state. This radically different scenario is consistent with a dissipative gapless state seen in experiments in neutral graphene. Interesting paired Hall states are possible, from residual interactions, in this SU(4) fermi sea with a small Zeeman spin polarization.