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

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.

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• Creation and Microscopic Origins of Single-Photon Emitters in Transition Metal Dichalcogenides and Hexagonal Boron Nitride
• The deep-acceptor nature of the chalcogen vacancies in 2D transition-metal dichalcogenides
• Proximity-enhanced valley Zeeman splitting at the WS${}_2$/graphene interface
• Reduced absorption due to defect-localized interlayer excitons in transition metal dichalcogenide-graphene heterostructures
• Ultra-Sensitive Extinction Measurements of Optically Active Defects in Monolayer MoS${}_2$
• Tunable electronic energy level alignment and exciton diversity in organic-inorganic van der Waals heterostructures
• Designable exciton mixing through layer alignment in WS${}_2$-graphene heterostructures
• Strain-induced exciton mobility in layered WS2 from first principles