Realization of an Interacting Two-Valley AlAs Bilayer System

TL;DR

This paper reports the creation of a bilayer AlAs system with electrons in different valleys, leading to unique quantum Hall states and negligible interlayer tunneling, demonstrated through magneto-transport experiments.

Contribution

It introduces a novel bilayer AlAs system with electrons in different valleys, enabling new quantum Hall phenomena and minimal interlayer tunneling.

Findings

Observation of a bilayer ν=1 quantum Hall state

Detection of a reentrant insulating phase

Negligible interlayer tunneling due to valley separation

Abstract

By using different widths for two AlAs quantum wells comprising a bilayer system, we force the X-point conduction-band electrons in the two layers to occupy valleys with different Fermi contours, electron effective masses, and g-factors. Since the occupied valleys are at different X-points of the Brillouin zone, the interlayer tunneling is negligibly small despite the close electron layer spacing. We demonstrate the realization of this system via magneto-transport measurements and the observation of a phase-coherent, bilayer $\nu$=1 quantum Hall state flanked by a reentrant insulating phase.