Nature of Valance Band Splitting on Multilayer MoS2

TL;DR

This study investigates the origins of valence band splitting in multilayer MoS2, highlighting the roles of intra-layer and inter-layer spin-orbit coupling and their dependence on layer number and pressure.

Contribution

It provides a detailed first-principles analysis of how spin-orbit and layer coupling effects influence valence band splitting in multilayer MoS2, including pressure effects.

Findings

Intra-layer spin-orbit coupling mainly causes valence band splitting at K.

Layer coupling widens the energy gap of split states in double-layer MoS2.

Inter-layer spin-orbit coupling increases under pressure, reducing the energy gap.

Abstract

Understanding the origin of splitting of valance band is important since it governs the unique spin and valley physics in few-layer MoS2. With first principle methods, we explore the effects of spin-orbit coupling and layer's coupling on few-layer MoS2. It is found that intra-layer spin-orbit coupling has a major contribution to the splitting of valance band at K. In double-layer MoS2, the layer's coupling results in the widening of energy gap of splitted states induced by intra-layer spin-orbit coupling. The valance band splitting of bulk MoS_2 in K can follow this model. We also find the effect of inter-layer spin-orbit coupling in triple-layer MoS2. In addition, the inter-layer spin-orbit coupling is found to become to be stronger under the pressure and results in the decrease of main energy gap in the splitting valance bands at K.