Quantized conductance in an AlAs 2D electron system quantum point contact

TL;DR

This paper presents experimental observations of quantized conductance in an AlAs quantum point contact, revealing valley degeneracy breaking and potential for valley filtering, along with indications of strong electron interactions.

Contribution

It demonstrates quantized conductance in an AlAs QPC with broken valley degeneracy and introduces a model for the energy levels considering in-plane valleys.

Findings

Weak conductance plateaus at integer multiples of 2e^2/h

Broken valley degeneracy in the QPC

Presence of a 0.7 anomaly suggestive of strong electron interactions

Abstract

We report experimental results on a quantum point contact (QPC) device formed in a wide AlAs quantum well where the two-dimensional electrons occupy two in-plane valleys with elliptical Fermi contours. To probe the closely-spaced, one-dimensional electric subbands, we fabricated a point contact device defined by shallow-etching and a top gate that covers the entire device. The conductance versus top gate bias trace shows a series of weak plateaus at integer multiples of $2e^2/h$, indicating a broken valley degeneracy in the QPC and implying the potential use of QPC as a simple "valley filter" device. A model is presented to describe the quantized energy levels and the role of the in-plane valleys in the transport. We also observe a well-developed conductance plateau near $0.7x2e^2/h$ which may reflect the strong electron-electron interaction in the system.