Protected valley states and generation of valley- and spin-polarized current in monolayer MA2Z4

TL;DR

This paper demonstrates that monolayer MA2Z4 materials have protected valley states and can generate highly valley- and spin-polarized currents using circularly polarized infrared light, enabling potential applications in optovalleytronic devices.

Contribution

It reveals that six monolayer MA2Z4 compounds are direct band-gap semiconductors with protected valley states and demonstrates their use in generating polarized currents with near 100% polarization.

Findings

Six MA2Z4 monolayers are direct band-gap semiconductors.

Circularly polarized light induces valley-selective transitions.

Device achieves nearly 100% valley- and spin-polarized current.

Abstract

The optical selection rules obeyed by two-dimensional materials with spin-valley coupling enable the selective excitation of carriers. We show that six members of the monolayer MA2Z4 (M = Mo and W; A = C, Si, and Ge; Z = N, P, and As) family are direct band-gap semiconductors with protected valley states and that circularly polarized infrared light can induce valley-selective inter-band transitions. Our optovalleytronic device demonstrates a close to 100% valley- and spin-polarized current under in-plane bias and circularly polarized infrared light, which can be exploited to encode, process, and store information.