TY  - JOUR
AU  - Ersfeld, Manfred
AU  - Volmer, Frank
AU  - Rathmann, Lars
AU  - Kotewitz, Luca
AU  - Heithoff, Maximilian
AU  - Lohmann, Mark
AU  - Yang, Bowen
AU  - Watanabe, Kenji
AU  - Taniguchi, Takashi
AU  - Bartels, Ludwig
AU  - Shi, Jing
AU  - Stampfer, Christoph
AU  - Beschoten, Bernd
TI  - Unveiling Valley Lifetimes of Free Charge Carriers in Monolayer WSe 2
JO  - Nano letters
VL  - 20
IS  - 5
SN  - 1530-6992
CY  - Washington, DC
PB  - ACS Publ.
M1  - FZJ-2020-02148
SP  - 3147 - 3154
PY  - 2020
AB  - 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).
LB  - PUB:(DE-HGF)16
C6  - pmid:32202802
UR  - <Go to ISI:>//WOS:000535255300027
DO  - DOI:10.1021/acs.nanolett.9b05138
UR  - https://juser.fz-juelich.de/record/877335
ER  -