Two-dimensional electrons occupying multiple valleys in AlAs

TL;DR

This paper reviews the physics of two-dimensional electrons in AlAs quantum wells, highlighting how valley occupation can be controlled to tune effective mass, g-factor, and anisotropy, enabling exploration of rich physical phenomena.

Contribution

It introduces methods to control valley occupation in AlAs quantum wells, allowing tunable electronic properties and enabling new physical investigations.

Findings

Valley occupation can be manipulated via well width and strain.

Tunable effective mass, g-factor, and anisotropy achieved.

Rich physics explored through controlled valley states.

Abstract

Two-dimensional electrons in AlAs quantum wells occupy multiple conduction-band minima at the X- points of the Brillouin zone. These valleys have large effective mass and g-factor compared to the stan-dard GaAs electrons, and are also highly anisotropic. With proper choice of well width and by applying symmetry-breaking strain in the plane, one can control the occupation of different valleys thus rendering a system with tuneable effective mass, g-factor, Fermi contour anisotropy, and valley degeneracy. Here we review some of the rich physics that this system has allowed us to explore.