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HL: Fachverband Halbleiterphysik
HL 18: 2D Materials and Heterostructures: Emerging Materials and Phenomena
HL 18.8: Talk
Tuesday, March 19, 2024, 11:30–11:45, EW 201
Strain control of hybridization between dark and localized excitons in a 2D semiconductor — •Pablo Hernández López1, Sebastian Heeg1, Christoph Schattauer2, Sviatoslav Kovalchuk3, Abhijeet Kumar3, Douglas J. Bock3, Jan N. Kirchhof3, Bianca Höfer3, Kyrylo Greben3, Denis Yagodkin3, Lukas Linhart2, and Florian Libisch2 — 1Department of Physics and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany — 2Vienna University of Technology, Vienna, Austria — 3Physics Department, Freie Universität Berlin, Berlin
Mechanical strain is a powerful tuning knob for excitons, Coulomb-bound electron-hole complexes dominating optical properties of two- dimensional semiconductors. While the strain response of bright free excitons is broadly understood, the behaviour of dark free excitons (long-lived excitations that couple weakly with light due to conservation laws) or localized excitons related to defects remains mostly unexplored. Here, we study the strain behaviour of these fragile many-body states on pristine suspended WSe2 kept at cryogenic temperatures. We find that upon straining, dark and localized excitons in monolayer WSe2 are brought into energetic resonance, forming a new hybrid state that inherits the properties of the constituent species. The characteristics of the hybridized state, including an order-of-magnitude enhanced light/matter coupling, avoided-crossing energy shifts, and strain tunability of many body interactions, are all supported by first-principles calculations. The hybridized exciton reported here may play a critical role in the operation of single quantum emitters based on WSe2.
Keywords: Strain engineering; Dark excitons; Defects in TMDCs; Monolayer WSe2; Hybridized states