Valley pseudospin in monolayer MoSi2N4 and MoSi2As4

TL;DR

This paper predicts valley-contrast properties and multiple-folded valleys in monolayer MoSi2N4 and MoSi2As4 using first-principles calculations, highlighting their potential for advanced valleytronic applications.

Contribution

It introduces the theoretical prediction of valley-contrast and multiple-folded valleys in these new 2D materials, expanding the understanding of valleytronics beyond traditional systems.

Findings

Valley-contrast properties can be realized in monolayer MoSi2N4 and MoSi2As4.

Valleys in MoSi2As4 are multiple-folded, indicating a new valley dimension.

A three-band low-power Hamiltonian describes the multiple-folded valleys.

Abstract

For a long time, two-dimensional (2D) hexagonal MoS2 was proposed as a promising material for valleytronic system. However, the limited size of growth and low carrier motilities in MoS2 restrict its further application. Very recently, a new kind of hexagonal 2D MXene, MoSi2N4, was successfully synthesized with large size, excellent ambient stability, and considerable hole mobility. In this paper, based on the first-principles calculations, we predict that the valley-contrast properties can be realized in monolayer MoSi2N4 and its derivative MoSi2As4. Beyond the traditional two-level valleys, the valleys in monolayer MoSi2As4 are multiple-folded, implying a new valley dimension. Such multiple-folded valleys can be described by a three-band low-power Hamiltonian. This study presents the theoretical advance and the potential applications of monolayer MoSi2N4 and MoSi2As4 in valleytronic devices, especially multiple information processing.