Quantum Hall effect in dual-gated graphene bilayers with tunable layer density imbalance

TL;DR

This study investigates the quantum Hall effect in dual-gated graphene bilayers, demonstrating how tunable layer density imbalance influences quantum Hall states and reveals interaction effects not predicted by simple theories.

Contribution

It provides experimental evidence of a tunable quantum Hall state at ν=0 and shows unexpected suppression of higher filling factor states with layer imbalance.

Findings

Quantum Hall state at ν=0 emerges with layer imbalance.

Suppression of ν=8 and ν=12 states at balanced layers.

Layer imbalance affects quantum Hall states beyond simple models.

Abstract

We study the magnetotransport properties of dual-gated graphene bilayers, in which the total density and layer density imbalance are independently controlled. As the bilayer is imbalanced we observe the emergence of a quantum Hall state (QHS) at filling factor $\nu=0$ evinced by a plateau in the Hall conductivity, consistent with the opening of a gap between the electron and hole bands. By varying the layer density imbalance at fixed total density, we observe a suppression of the QHS at filling factors $\nu=8$ and $\nu=12$ when the layer densities are balanced, an observation at variance with theoretical expectations in the absence of electron-electron interaction and disorder.