Tunable magneto-optical properties in MoS$_2$ via defect-induced exciton transitions

TL;DR

This paper investigates how chalcogen vacancies in monolayer MoS$_2$ influence exciton magnetic properties, revealing that defect engineering can tune the material's magneto-optical responses through complex excitonic interactions.

Contribution

It provides a theoretical framework showing how defect-induced excitonic states in MoS$_2$ can be controlled to modify magneto-optical properties, advancing defect engineering in 2D materials.

Findings

Variety of g-factors with different magnitudes and signs depending on exciton energy.

Defect architecture enables tuning of exciton magnetic response.

Hybridized electron-hole transitions reduce valley and spin selectivity.

Abstract

The presence of chalcogen vacancies in monolayer transition metal dichalcogenides (TMDs) leads to excitons with mixed localized-delocalized character and to reduced valley selectivity. Recent experimental advances in defect design in TMDs allow for a close examination of such mixed exciton states as a function of their degree of circular polarization under external magnetic fields, revealing strongly varying defect-induced magnetic properties. A theoretical understanding of these observations and their physical origins demands a predictive, structure-sensitive theory. In this work, we study the effect of chalcogen vacancies on the exciton magnetic properties in monolayer MoS$_2$. Using many-body perturbation theory, we show how the complex excitonic picture associated with the presence of defects -- with reduced valley and spin selectivity due to hybridized electron-hole transitions -- leads to structurally-controllable exciton magnetic response. We find a variety of g-factors with changing magnitudes and sign depending on the exciton energy and character. Our findings suggest a pathway to tune the nature of the excitons -- and by that their magneto-optical properties -- through defect architecture.