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Temporal Evolution of Low-Temperature Phonon Sidebands in Transition Metal Dichalcogenides
ACS Photonics ( IF 6.5 ) Pub Date : 2020-09-04 , DOI: 10.1021/acsphotonics.0c00866
Roberto Rosati 1 , Koloman Wagner 2 , Samuel Brem 1 , Raül Perea-Causín 1 , Edith Wietek 2 , Jonas Zipfel 2 , Jonas D. Ziegler 2 , Malte Selig 3 , Takashi Taniguchi 4 , Kenji Watanabe 5 , Andreas Knorr 3 , Alexey Chernikov 2 , Ermin Malic 1
Affiliation  

Low-temperature photoluminescence (PL) of hBN-encapsulated monolayer tungsten diselenide (WSe2) shows a multitude of sharp emission peaks below the bright exciton. Some of them have been recently identified as phonon sidebands of momentum-dark states. However, the exciton dynamics behind the emergence of these sidebands has not been revealed yet. In this joint theory–experiment study, we theoretically predict and experimentally observe time-resolved PL, providing microscopic insights into the thermalization of hot excitons formed after optical excitation. In very good agreement between theory and experiment, we demonstrate a spectral red-shift of phonon sidebands on a time scale of tens of picoseconds, reflecting the phonon-driven thermalization of hot excitons in momentum-dark states. Furthermore, we predict the emergence of a transient phonon sideband that vanishes in the stationary PL. The obtained microscopic insights are applicable to a broad class of 2D materials with multiple exciton valleys.

中文翻译:

过渡金属二硫属化物中低温声子边带的时间演化

hBN封装的单层二硒化钨(WSe 2的低温光致发光(PL))在明亮的激子下方显示出许多尖锐的发射峰。其中一些最近被确定为动量暗态的声子边带。然而,这些边带出现背后的激子动力学尚未被揭示。在这项理论与实验的联合研究中,我们从理论上预测并实验观察了时间分辨的PL,从而为光学激发后形成的热激子的热化提供了微观见解。在理论和实验之间取得很好的一致性,我们证明了声子边带在几十皮秒的时间尺度上的光谱红移,反映了声子驱动的热激子在动量暗态下的热化。此外,我们预测在固定PL中消失的瞬变声子边带的出现。
更新日期:2020-10-21
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