Symmetry, distorted bandstructure, and spin-orbit coupling of (group-III) metal-monochalcogenide monolayers

TL;DR

This paper investigates the electronic properties of group-III metal-monochalcogenide monolayers, revealing unique band distortions and spin-orbit effects, and explains these features using group theory and tight-binding models.

Contribution

It introduces a detailed analysis of the unusual band structure and spin phenomena in these monolayers, combining group theory with tight-binding calculations.

Findings

Identification of a 'caldera'-shaped valence band dispersion

Demonstration of spin splitting and spin-mixing driven by spin-orbit coupling

Calculation of band-edge g-factors and optical absorption spectra

Abstract

The electronic structure of (group-III) metal-monochalcogenide monolayers exhibits many unusual features. Some, such as the unusually distorted upper valence band dispersion we describe as a 'caldera', are primarily the result of purely orbital interactions. Others, including spin splitting and wavefunction spin-mixing, are directly driven by spin-orbit coupling. We employ elementary group theory to explain the origins of these properties, and use a tight-binding model to calculate the phenomena enabled by them, such as band-edge carrier effective g-factors, optical absorption spectrum, conduction electron spin orientation, and a relaxation-induced upper valence band population inversion and spin polarization mechanism.