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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 dichalcogenides — Zhao 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 Finley2 — 1Institute 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