Electronic structure, spin-orbit coupling, and interlayer interaction in bulk MoS2 and WS2

TL;DR

This study combines experimental ARPES measurements and first-principles calculations to analyze the electronic structure, spin-orbit effects, and interlayer interactions in bulk MoS2 and WS2, clarifying their contributions to band splitting.

Contribution

It provides a detailed comparison of experimental and theoretical results, clarifies the weak interlayer interaction in WS2, and links band gap trends to valence-band splitting and lattice parameters.

Findings

Interlayer interaction weakly affects valence band splitting in WS2

Band gap decreases with increasing valence-band splitting and molecular mass

Experimental results align with first-principles calculations

Abstract

We present in-depth measurements of the electronic band structure of the transition-metal dichalcogenides (TMDs) MoS2 and WS2 using angle-resolved photoemission spectroscopy, with focus on the energy splittings in their valence bands at the K point of the Brillouin zone. Experimental results are interpreted in terms of our parallel first-principles computations. We find that interlayer interaction only weakly contributes to the splitting in bulk WS2, resolving previous debates on its relative strength. We additionally find that across a range of TMDs, the band gap generally decreases with increasing magnitude of the valence-band splitting, molecular mass, or ratio of the out-of-plane to in-plane lattice constant. Our results provide an important reference for future studies of electronic properties of MoS2 and WS2 and their applications in spintronics and valleytronics devices.