Spontaneous Gully Polarized Quantum Hall States in ABA Trilayer Graphene

TL;DR

This paper investigates how electric and magnetic fields influence the formation and interaction-driven breakdown of Dirac gullies in ABA trilayer graphene, revealing a spontaneous nematic quantum Hall state.

Contribution

It demonstrates the controllable emergence of Dirac gullies and their interaction-induced symmetry breaking in ABA trilayer graphene through magnetotransport experiments.

Findings

Identification of Lifshitz transitions indicating Dirac gullies formation

Observation of increased Landau level degeneracy at high electric fields

Evidence of a spontaneously broken rotational symmetry in the quantum Hall regime

Abstract

Bernal-stacked multilayer graphene is a versatile platform to explore quantum transport phenomena and interaction physics due to its exceptional tunability via electrostatic gating. For instance, upon applying a perpendicular electric field, its band structure exhibits several off-center Dirac points (so-called Dirac gullies) in each valley. Here, the formation of Dirac gullies and the interaction-induced breakdown of gully coherence is explored via magnetotransport measurements in high-quality Bernal-stacked (ABA) trilayer graphene. In the absence of a magnetic field, multiple Lifshitz transitions as function of electric field and charge carrier density indicating the formation of Dirac gullies are identified. In the quantum Hall regime and high electric fields, the emergence of Dirac gullies is evident as an increase in Landau level degeneracy. When tuning both electric and magnetic fields, electron-electron interactions can be controllably enhanced until the gully degeneracy is eventually lifted. The arising correlated ground state is consistent with a previously predicted nematic phase that spontaneously breaks the rotational gully symmetry.