Valley Degree of Freedom in Two-Dimensional van der Waals Materials

TL;DR

This paper reviews the physics, detection, and manipulation of valley degrees of freedom in layered van der Waals materials, highlighting their potential for quantum and classical information processing.

Contribution

It provides a comprehensive survey of valley polarization physics, spectroscopic techniques, and recent device applications in layered materials.

Findings

Valley polarization can be achieved and detected using spectroscopic methods.

Manipulation of valley degrees of freedom enables potential device applications.

Recent advances demonstrate control of valley states for information processing.

Abstract

Layered materials can possess valleys that are indistinguishable from one another except for the momentum. These valleys are individually addressable in momentum space at the K and K' points in the first Brillouin zone. Such valley addressability opens up the possibility of utilizing the momentum state of quasi-particles as a completely new paradigm in quantum and classical information processing. This review focuses on the physics behind valley polarization and talks about carriers of valley degree of freedom (VDF) in layered materials. Then we provide a detailed survey of simple spectroscopic techniques commonly utilized to identify and manipulate valley polarization in van der Waals layered materials. Finally, we conclude with the recent developments towards the manipulation of VDF for device application and associated challenges.