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HL: Fachverband Halbleiterphysik

HL 18: 2D Materials and Heterostructures: Emerging Materials and Phenomena

HL 18.7: Talk

Tuesday, March 19, 2024, 11:15–11:30, EW 201

Srain control of exciton and trion spin-valley dynamics in monolayer transition metal dichalcogenidesZhao An1, Pedro Soubelet2, Yaroslav Zhumagulov3, Michael Zopf1, •Alex Delhomme2, Chenjiang Qian2, Paulo Faria Junior3, Jaroslav Fabian3, Xin Cao1, Jingzhong Yang1, Andreas Stier2, Fei Ding1, and Jonathan Finley21Institute of Solid State Physics, Leibniz Universitat Hannover, Appelstraße 2, 30167 Hannover, Germany — 2Walter Schottky Institut and TUM School of Natural Sciences, Technische Universitat Munchen, Am Coulombwall 4, 85748 Garching, Germany — 3Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany.

The electron-hole exchange interaction is a fundamental mechanism that drives valley depolarization via intervalley exciton hopping in semiconductor multivalley systems. Here, we report polarization-resolved photoluminescence spectroscopy of neutral excitons and negatively charged trions in monolayer MoSe2 and WSe2 under biaxial strain. We observe a marked enhancement (reduction) on the WSe2 triplet trion valley polarization with compressive (tensile) strain while the trion in MoSe2 is unaffected. The origin of this effect is shown to be a strain-dependent tuning of the electron-hole exchange interaction. A combined analysis of the strain-dependent polarization degree using ab initio calculations and rate equations shows that strain affects intervalley scattering beyond what is expected from strain-dependent band-gap modulations. The results evidence how strain can be used to tune valley physics in energetically degenerate multivalley systems.

Keywords: Strain tuning; Exciton spin-valley dynamics; Electron-hole exchange interaction

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