Realization of a Valley Superlattice

TL;DR

This paper demonstrates a method to create a valley superlattice in an AlAs quantum well by using a strain grating, enabling control over valley polarization for potential valleytronic applications.

Contribution

It introduces a novel technique to engineer a valley superlattice through strain modulation, advancing valley control in multi-valley materials.

Findings

Successful fabrication of a strain-induced valley superlattice

Demonstration of spatial modulation of valley populations

Potential for valley-selective device applications

Abstract

In a number of widely-studied materials, such as Si, AlAs, Bi, graphene, MoS2, and many transition metal dichalcogenide monolayers, electrons acquire an additional, spin-like degree of freedom at the degenerate conduction band minima, also known as "valleys". External symmetry breaking fields such as mechanical strain, or electric or magnetic fields, can tune the valley-polarization of these materials making them suitable candidates for "valleytronics". Here we study a quantum well of AlAs, where the two-dimensional electrons reside in two energetically degenerate valleys. By fabricating a strain-inducing grating on the sample surface, we engineer a spatial modulation of the electron population in different valleys, i.e., a "valley superlattice" in the quantum well plane. Our results establish a novel manipulation technique of the valley degree of freedom, paving the way to realizing a valley-selective layered structure in multi-valley materials, with potential application in valleytronics.