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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 Libisch21Department 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

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