Role of density imbalance in an interacting bilayer hole system

TL;DR

This study investigates how density imbalance affects phase transitions in interacting GaAs hole bilayers, revealing the robustness of the quantum Hall state and the emergence of hysteresis indicating a first-order transition.

Contribution

It demonstrates the impact of layer density imbalance on quantum Hall states and insulating phases in bilayer hole systems, highlighting a new aspect of phase behavior.

Findings

Quantum Hall state strengthens with charge transfer between layers.

Insulating phases vanish as density imbalance increases.

Hysteresis indicates a first-order quantum phase transition.

Abstract

We study interacting GaAs hole bilayers in the limit of zero tunneling. When the layers have equal densities, we observe a phase coherent bilayer quantum Hall (QH) state at total filling factor $\nu=1$, flanked by insulating phases at nearby fillings which suggest the formation of a pinned, bilayer Wigner crystal. As we transfer charge from one layer to another, the insulating phases disappear while, surprisingly, the $\nu=1$ QH state becomes stronger. Concomitantly, a pronounced hysteresis develops in the longitudinal magnetoresistance at higher fillings, indicative of a first-order quantum phase transition.