Unveiling valley lifetimes of free charge carriers in monolayer WSe$_2$
| Autor: | Ersfeld, Manfred, Volmer, Frank, Rathmann, Lars, Kotewitz, Luca, Heithoff, Maximilian, Lohmann, Mark, Yang, Bowen, Watanabe, Kenji, Taniguchi, Takashi, Bartels, Ludwig, Shi, Jing, Stampfer, Christoph, Beschoten, Bernd |
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| Rok vydání: | 2019 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1021/acs.nanolett.9b05138 |
| Popis: | We report on nanosecond long, gate-dependent valley lifetimes of free charge carriers in monolayer WSe$_2$, 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 WSe$_2$ 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). Comment: 22 pages, 13 figures |
| Databáze: | arXiv |
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