Article (Scientific journals)
Ab Initio Calculations of Ultrashort Carrier Dynamics in Two-Dimensional Materials: Valley Depolarization in Single-Layer WSe2
Molina-Sanchez, Alejandro; Sangalli, Davide; Wirtz, Ludger et al.
2017In Nano Letters, 17, p. 4549
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Keywords :
valley physics; 2D materials; carrier-dynamics; time-dependent spectroscopy; ab-initio calculations
Abstract :
[en] In single-layer WSe2, a paradigmatic semiconducting transition metal dichalcogenide, a circularly polarized laser field can selectively excite electronic transitions in one of the inequivalent K± valleys. Such selective valley population corresponds to a pseudospin polarization. This can be used as a degree of freedom in a “valleytronic” device provided that the time scale for its depolarization is sufficiently large. Yet, the mechanism behind the valley depolarization still remains heavily debated. Recent time–dependent Kerr experiments have provided an accurate way to visualize the valley dynamics by measuring the rotation of a linearly polarized probe pulse applied after a circularly polarized pump pulse. We present here a clear, accurate and parameter–free description of the valley dynamics. By using an atomistic, ab initio approach we fully disclose the elemental mechanisms that dictate the depolarization effects. Our results are in excellent agreement with recent time–dependent Kerr experiments. We explain the Kerr dynamics and its temperature dependence in terms of electron–phonon me- diated processes that induce spin–flip inter–valley transitions.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Molina-Sanchez, Alejandro ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Sangalli, Davide
Wirtz, Ludger ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Marini, Andrea
External co-authors :
yes
Language :
English
Title :
Ab Initio Calculations of Ultrashort Carrier Dynamics in Two-Dimensional Materials: Valley Depolarization in Single-Layer WSe2
Publication date :
14 July 2017
Journal title :
Nano Letters
ISSN :
1530-6992
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
17
Pages :
4549
Peer reviewed :
Peer Reviewed verified by ORBi
Focus Area :
Physics and Materials Science
European Projects :
H2020 - 676598 - MaX - Materials design at the eXascale
FnR Project :
FNR7731521 - #4;modelling Of Carrier Dynamics And Ultra-fast Spectroscopy In Two-dimensional Materials, 2014 (01/12/2014-31/03/2017) - Alejandro Molina-sánchez
Funders :
CE - Commission Européenne [BE]
Available on ORBilu :
since 08 September 2017

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