Control of Valley Degeneracy in MoS2 by Layer Thickness and Electric Field and Its Effect on Thermoelectric Properties

TL;DR

This study explores how layer thickness and electric fields in MoS2 influence valley degeneracy and thermoelectric properties, revealing tunable Seebeck coefficient and power factor for potential thermoelectric applications.

Contribution

It demonstrates control over valley degeneracy in MoS2 via layer thickness and electric field, impacting thermoelectric performance, which is a novel approach in 2D materials research.

Findings

Valley degeneracy varies with layer number and electric field.

Maximum power factor achieved in monolayer and bilayer MoS2.

Seebeck coefficient and conductivity can be independently tuned.

Abstract

We have investigated the valley degeneracy of MoS2 multilayers and its effect on thermoelectric properties. By modulating the layer thickness and external electric field, the hole valleys at {\Gamma} and K points in the highest energy valence band and the electron valleys at K and {\Sigma}min points in the lowest energy conduction band are shifted differently. The hole valley degeneracy is observed in MoS2 monolayer, while that of electron valley is in MoS2 bilayer and monolayer under the external electric field. By tuning the valley degeneracy, the Seebeck coefficient and electrical conductivity can be separately controlled, and the maximum power factor can be obtained in n-type (p-type) MoS2 monolayer with (without) the external electric field. We suggest that the transition metal dichalcogenides are good example to investigate the role of valley degeneracy in the thermoelectric and optical properties with the control of interlayer interaction and external electric field strength.