Role of density imbalance in an interacting bilayer hole system

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.