Emergent Dirac gullies and gully-symmetry breaking quantum Hall states in ABA trilayer graphene

TL;DR

This study uses quantum capacitance measurements to explore how electron interactions and symmetry breaking in ABA trilayer graphene lead to emergent Dirac gullies and novel quantum Hall states.

Contribution

It reveals the formation of Dirac gullies and associated symmetry-breaking quantum Hall states in ABA trilayer graphene under high displacement fields and low magnetic fields.

Findings

Emergence of Dirac gullies near Brillouin zone corners.

Landau level degeneracy change from two to three.

Observation of Coulomb-driven nematic phases.

Abstract

We report on quantum capacitance measurements of high quality, graphite- and hexagonal boron nitride encapsulated Bernal stacked trilayer graphene devices. At zero applied magnetic field, we observe a number of electron density- and electrical displacement-tuned features in the electronic compressibility associated with changes in Fermi surface topology. At high displacement field and low density, strong trigonal warping gives rise to emergent Dirac gullies centered near the corners of the hexagonal Brillouin and related by three fold rotation symmetry. At low magnetic fields of $B=1.25$~T, the gullies manifest as a change in the degeneracy of the Landau levels from two to three. Weak incompressible states are also observed at integer filling within these triplets Landau levels, which a Hartree-Fock analysis indicates are associated with Coulomb-driven nematic phases that spontaneously break rotation symmetry.