Photoinduced valley-polarized current of layered MoS2 by electric tuning

TL;DR

This study demonstrates how circularly polarized light and gate voltage can control valley-polarized currents in layered MoS2 transistors, revealing tunable valley polarization effects with potential for valleytronic applications.

Contribution

First-principles analysis showing electric and optical tuning of valley-polarized currents in monolayer and bilayer MoS2, including asymmetric behavior in bilayers.

Findings

Valley polarization reaches ±1.0 in monolayer MoS2.

Gate voltage modulates valley polarization.

Asymmetric polarization behavior observed in bilayer MoS2.

Abstract

A photoinduced current of a layered MoS2-based transistor is studied from first-principles. Under the illumination of circular polarized light, a valley-polarized current is generated, which can be tuned by the gate voltage. For monolayer MoS2, the valley-polarized spin-up (down) electron current at K (K') points is induced by the right (left) circular polarized light. The valley polarization is found to reach +1.0 (-1.0) for the valley current that carried such a K (K') index. For bilayer MoS2, the spin-up (down) current can be induced at both K and K' valleys by the right (left) circular light. In contrast to monolayer MoS2, the photoinduced valley polarization shows asymmetric behavior upon reversal of the gate voltage. Our results show that the valley polarization of the photoinduced current can be modulated by the circular polarized light and the gate voltage. All the results can be well understood using a simple kp model.