Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers

• Published in: 2d materials Vol. 3; no. 3; p. 35009
• Main Authors: Slobodeniuk, A O, Basko, D M
• Format: Journal Article
• Language: English
• Published: IOP Publishing 12.08.2016
• Subjects: Condensed Matter; Decay; Decay rate; decay rate of dark excitons; Electric fields; Electron spin; electronic and optical properties; Electronics; Excitons; Materials Science; Mesoscopic Systems and Quantum Hall Effect; Monolayers; Physics; Quantum Physics; transition metal dichalcogenide monolayers; Transition metals
• ISSN: 2053-1583; 2053-1583
• DOI: 10.1088/2053-1583/3/3/035009

We perform a theoretical study of radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers. This decay necessarily involves an electronic spin flip. The intrinsic decay mechanism due to interband spin-flip dipole moment perpendicular to the monolayer plane, gives a rate about 100-1000 times smaller than that of bright excitons. However, we find that this mechanism also introduces an energy splitting due to a local field effect, and the whole oscillator strength is contained in the higher-energy component, while the lowest-energy state remains dark and needs an extrinsic spin-flip mechanism for the decay. Rashba effect due to a perpendicular electric field or a dielectric substrate, gives a negligible radiative decay rate (about 107 times slower than that of bright excitons). Spin flip due to Zeeman effect in a sufficiently strong in-plane magnetic field can give a decay rate comparable to that due to the intrinsic interband spin-flip dipole.