Tunable symmetries of integer and fractional quantum Hall phases in heterostructures with multiple Dirac bands

TL;DR

This study maps the phase diagram of ABA-stacked trilayer graphene in quantum Hall conditions, revealing tunable symmetries and fractional quantum Hall states affected by interlayer potential.

Contribution

It provides the first detailed experimental mapping of symmetry transitions and fractional quantum Hall states in multilayer graphene with multiple Dirac bands.

Findings

Transitions among spin, valley, orbital, and parity polarizations observed.

Fractional quantum Hall states at filling factors 2/3 and -11/3 identified.

Interlayer potential destabilizes certain fractional quantum Hall states.

Abstract

The co-presence of multiple Dirac bands in few-layer graphene leads to a rich phase diagram in the quantum Hall regime. Using transport measurements, we map the phase diagram of BN-encapsulated ABA-stacked trilayer graphene as a function charge density n, magnetic field B and interlayer displacement field D, and observe transitions among states with different spin, valley, orbital and parity polarizations. Such rich pattern arises from crossings between Landau levels from different subbands, which reflect the evolving symmetries that are tunable in situ. At D=0, we observe fractional quantum Hall (FQH) states at filling factors 2/3 and -11/3. Unlike those in bilayer graphene, these FQH states are destabilized by a small interlayer potential that hybridizes the different Dirac bands.