# Narrow-band anisotropic electronic structure of ReS$_2$

## TL;DR

This study uses angle-resolved photoemission spectroscopy and density-functional theory to reveal the highly anisotropic, quasi-one-dimensional electronic structure of ReS$_2$, highlighting the effects of structural distortion and spin-orbit coupling.

## Contribution

It provides detailed experimental and theoretical insights into the anisotropic electronic structure of ReS$_2$, emphasizing the influence of crystal distortion and spin-orbit effects.

## Key findings

- ReS$_2$ exhibits narrow valence bands due to structural distortion and spin-orbit coupling.
- The electronic structure shows strong in-plane anisotropy with quasi-one-dimensional bands.
- The valence band character transitions to a more three-dimensional form near the top.

## Abstract

We have used angle resolved photoemission spectroscopy to investigate the band structure of ReS$_2$, a transition-metal dichalcogenide semiconductor with a distorted 1T crystal structure. We find a large number of narrow valence bands, which we attribute to the combined influence of the structural distortion and spin-orbit coupling. We further image how this leads to a strong in-plane anisotropy of the electronic structure, with quasi-one-dimensional bands reflecting predominant hopping along zig-zag Re chains. We find that this does not persist up to the top of the valence band, where a more three-dimensional character is recovered with the fundamental band gap located away from the Brillouin zone centre along $k_z$. These experiments are in good agreement with our density-functional theory calculations, shedding new light on the bulk electronic structure of ReS$_2$, and how it can be expected to evolve when thinned to a single layer.