%0 Journal Article
%A Ersfeld, Manfred
%A Volmer, Frank
%A Rathmann, Lars
%A Kotewitz, Luca
%A Heithoff, Maximilian
%A Lohmann, Mark
%A Yang, Bowen
%A Watanabe, Kenji
%A Taniguchi, Takashi
%A Bartels, Ludwig
%A Shi, Jing
%A Stampfer, Christoph
%A Beschoten, Bernd
%T Unveiling Valley Lifetimes of Free Charge Carriers in Monolayer WSe 2
%J Nano letters
%V 20
%N 5
%@ 1530-6992
%C Washington, DC
%I ACS Publ.
%M FZJ-2020-02148
%P 3147 - 3154
%D 2020
%X We report on nanosecond-long, gate-dependent valley lifetimes of free charge carriers in monolayer WSe2, unambiguously identified by the combination of time-resolved Kerr rotation and electrical transport measurements. While the valley polarization increases when tuning the Fermi level into the conduction or valence band, there is a strong decrease of the respective valley lifetime consistent with both electron-phonon and spin-orbit scattering. The longest lifetimes are seen for spin-polarized bound excitons in the band gap region. We explain our findings via two distinct, Fermi-level-dependent scattering channels of optically excited, valley-polarized bright trions either via dark or bound states. By electrostatic gating we demonstrate that the transition-metal dichalcogenide WSe2 can be tuned to be either an ideal host for long-lived localized spin states or allow for nanosecond valley lifetimes of free charge carriers (>10 ns).
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:32202802
%U <Go to ISI:>//WOS:000535255300027
%R 10.1021/acs.nanolett.9b05138
%U https://juser.fz-juelich.de/record/877335