Theory of strain in single-layer transition metal dichalcogenides

TL;DR

This paper develops a comprehensive theoretical framework to analyze how strain affects the electronic properties of single-layer transition metal dichalcogenides, including band structure modifications and spin-strain interactions.

Contribution

It introduces a full tight-binding model and an effective low-energy model to describe strain effects in these 2D materials, incorporating second-order momentum and strain terms.

Findings

Strain shifts electron and hole band edges.

Solutions can be modeled as harmonic oscillator and double quantum well.

Spin-strain coupling plays a significant role.

Abstract

Strain engineering has emerged as a powerful tool to modify the optical and electronic properties of two-dimensional crystals. Here we perform a systematic study of strained semiconducting transition metal dichalcogenides. The effect of strain is considered within a full Slater-Koster tight-binding model, which provides us with the band structure in the whole Brillouin zone. From this, we derive an effective low-energy model valid around the K point of the BZ, which includes terms up to second order in momentum and strain. For a generic profile of strain, we show that the solutions for this model can be expressed in terms of the harmonic oscillator and double quantum well models, for the valence and conduction bands respectively. We further study the shift of the position of the electron and hole band edges due to uniform strain. Finally, we discuss the importance of spin-strain coupling in these 2D semiconducting materials.