Quasiparticle Band Gaps, Excitonic Effects, and Anisotropic Optical Properties of Monolayer Distorted 1-T Diamond-chain Structures

TL;DR

This study uses many-body perturbation theory to reveal how electronic and optical properties of distorted 1-T ReS2 and ReSe2 monolayers differ from previous predictions, highlighting their potential for optoelectronic applications.

Contribution

It provides the first comprehensive many-body perturbation theory analysis of excited-state properties of distorted 1-T ReS2 and ReSe2 monolayers, showing significant band gap corrections and novel excitonic behaviors.

Findings

Quasiparticle band gaps are substantially increased by electronic self-energy.

Monolayer ReSe2 is converted to a direct-gap semiconductor.

Distinct polarization dependence of excitons in ReS2 and ReSe2.

Abstract

We report many-body perturbation theory calculations of excited-state properties of distorted 1-T diamond-chain monolayer rhenium disulfide (ReS2) and diselenide (ReSe2). Electronic self-energy substantially enhances their quasiparticle band gaps and, surprisingly, converts monolayer ReSe2 to a direct-gap semiconductor, which was, however, regarded to be an indirect one by density-functional-theory calculations. Their optical absorption spectra are dictated by strongly bound excitons. Unlike hexagonal structures, the lowest-energy bright exciton of distorted 1-T ReS2 exhibits a perfect figure-8 shape polarization dependence but those of ReSe2 only exhibit a partial polarization dependence, which results from two nearly-degenerated bright excitons whose polarization preferences are not aligned. Our first-principles calculations are in agreement with experiments and pave the way for optoelectronic applications.