講演情報
[18p-D61-17]Long-lived valley-polarization in suspended WSe2 monolayers strained by electrostatic pressure
〇Giacomo Mariani1, Yoji Kunihashi1, Louis Smet1, Taro Wakamura1, Satoshi Sasaki1, Jun Ishihara2, Makoto Kohda2, Junsaku Nitta1,2, Haruki Sanada1 (1.NTT-BRL, 2.Tohoku Univ.)
キーワード：
monolayer、transition-metal dichalcogenides、kerr rotation
Transition-metal dichalcogenides (TMDs) monolayers have been emerging as a platform for hybridizing spintronics, valleytronics, and optoelectronics because of their direct bandgap and spin-valley-dependent optical transitions. However, the properties of TMD monolayers are sensitive to the interfacial inhomogeneities with their supporting substrate. Impurities and strain puddles create potential traps for charges which can affect the valley polarization. Previous studies evidenced that suspended monolayers have improved carrier mobility and are less sensitive to the dielectric screening of the substrate. However, the dynamics of the valley polarization of suspended monolayers have been mainly studied by photoluminescence (PL) spectroscopy, which limits the analysis to short-lived bright excitons and radiatively recombined carriers. We report the long lifetime of the valley polarization in a suspended WSe2 monolayer by a pump-probe Kerr rotation (KR) spectroscopy, measured at a temperature of 7 K. Compared to PL analysis, the KR signal is sensitive to both the radiative and non-radiative recombinations and thus can measure the valley polarization of long-lived complexes such as trions or resident carriers.
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