# Valley-Layer Coupling: A New Design Principle for Valleytronics

## TL;DR

This paper introduces valley-layer coupling (VLC) in 2D materials, enabling electric control of valley polarization and revealing new optical phenomena, thus advancing valleytronics technology.

## Contribution

The paper proposes the concept of valley-layer coupling (VLC), demonstrating its potential for electric control of valley polarization in 2D materials through first-principles calculations.

## Key findings

- VLC enables switchable valley polarization control.
- Systems with VLC exhibit valley-contrasting linear dichroism.
- VLC allows optical selection of interlayer exciton polarization.

## Abstract

We introduce the concept of valley-layer coupling (VLC) in two-dimensional materials, where the low-energy electronic states in the emergent valleys have valley-contrasted layer polarization such that each state is spatially localized on the top or bottom super-layer. The VLC enables a direct coupling between valley and gate electric field, opening a new route towards electrically controlled valleytronics. We analyze the symmetry requirements for the system to host VLC, demonstrate our idea via first-principles calculations and model analysis of a concrete 2D material example, and show that an electric, continuous, wide-range, and switchable control of valley polarization can be achieved by VLC. Furthermore, we find that systems with VLC can exhibit other interesting physics, such as valley-contrasting linear dichroism and optical selection of the electric polarization of interlayer excitons.