Interaction-induced Interlayer Charge Transfer in the Extreme Quantum Limit

TL;DR

This study investigates how strong electron-electron interactions in a bilayer system under extreme magnetic fields cause unusual interlayer charge transfer behaviors, including oscillations, anomalies, and effects of electron condensation.

Contribution

It reveals novel interaction-induced charge transfer phenomena in bilayer systems at high magnetic fields, especially near the quantum limit, and uncovers the role of composite fermions and Wigner crystal formation.

Findings

Layer densities oscillate with magnetic field due to Landau level alignment.

Anomalous charge transfer occurs at the quantum limit, favoring the majority layer.

Screening effects from composite fermions influence charge transfer in dilute layers.

Abstract

An interacting bilayer electron system provides an extended platform to study electron-electron interaction beyond single layers. We report here experiments demonstrating that the layer densities of an asymmetric bilayer electron system oscillate as a function of perpendicular magnetic field that quantizes the energy levels. At intermediate fields, this interlayer charge transfer can be well explained by the alignment of the Landau levels in the two layers. At the highest fields where both layers reach the extreme quantum limit, however, there is an anomalous, enhanced charge transfer to the majority layer. Surprisingly, when the minority layer becomes extremely dilute, this charge transfer slows down as the electrons in the minority layer condense into a Wigner crystal. Furthermore, by examining the quantum capacitance of the dilute layer at high fields, the screening induced by the composite fermions in an adjacent layer is unveiled. The results highlight the influence of strong interaction in interlayer charge transfer in the regime of very high fields and low Landau level filling factors.