Spin states protected from intrinsic electron-phonon coupling reaching 100 ns lifetime at room temperature in MoSe₂
Ersfeld, Manfred (RWTH Aachen University)
Volmer, Frank (RWTH Aachen University)
Melo, Pedro Miguel M. C. de (Université de Liège. Complex and Entangled Systems from Atoms to Materials)
Winter, Robin de (RWTH Aachen University)
Heithoff, Maximilian (RWTH Aachen University)
Zanolli, Zeila (Institut Català de Nanociència i Nanotecnologia)
Stampfer, Cristoph (RWTH Aachen University)
Verstraete, Matthieu J. (Université de Liège. Complex and Entangled Systems from Atoms to Materials)
Beschoten, Bernd (RWTH Aachen University)

Data:	2019
Resum:	We present time-resolved Kerr rotation measurements, showing spin lifetimes of over 100 ns at room temperature in monolayer MoSe. These long lifetimes are accompanied by an intriguing temperature-dependence of the Kerr amplitude, which increases with temperature up to 50 K and then abruptly switches sign. Using ab initio simulations, we explain the latter behavior in terms of the intrinsic electron-phonon coupling and the activation of transitions to secondary valleys. The phonon-assisted scattering of the photoexcited electron-hole pairs prepares a valley spin polarization within the first few ps after laser excitation. The sign of the total valley magnetization, and thus the Kerr amplitude, switches as a function of temperature, as conduction and valence band states exhibit different phonon-mediated intervalley scattering rates. However, the electron-phonon scattering on the ps time scale does not provide an explanation for the long spin lifetimes. Hence, we deduce that the initial spin polarization must be transferred into spin states, which are protected from the intrinsic electron-phonon coupling, and are most likely resident charge carriers, which are not part of the itinerant valence or conduction band states.
Ajuts:	European Commission 824143 European Commission 785219 European Commission 653838 Ministerio de Economía y Competitividad SEV-2017-0706 Ministerio de Economía y Competitividad RYC-2016-19344 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1506
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió sotmesa a revisió
Matèria:	Transition metal dichalcogenides ; Monolayer MoSe₂ ; Time-resolved Kerr rotation ; Spin lifetime ; Electron−phonon coupling
Publicat a:	Nano letters, Vol. 19, issue 6 (June 2019) , p. 4083-4090, ISSN 1530-6992

DOI: 10.1021/acs.nanolett.9b01485
PMID: 31063385

Preprint 10 p, 2.0 MB

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