Phonon-Assisted Intervalley Scattering Determines Ultrafast Exciton Dynamics in MoSe2 Bilayers
Phonon-Assisted Intervalley Scattering Determines Ultrafast Exciton Dynamics in MoSe2 Bilayers
复制标题
DOI：
10.1103/physrevlett.127.157403
复制
发表时间：
2021-10-08
影响因子：
8.6
通讯作者：
Li, Xiaoqin
中科院分区：
文献类型：
--
作者：
Helmrich, Sophia;Sampson, Kevin;Li, Xiaoqin
虽然固体的所有能带结构中都存在谷（能量极值），但它们在确定原子薄过渡金属二硫属化物 (TMDC) 的激子共振和动力学方面的卓越作用是独一无二的。使用二维相干电子光谱，我们发现 MoSe2 双层中激子退相干发生的时间尺度比单层中快得多。我们进一步确定了双层中的两种群体弛豫通道，一种相干通道和一种非相干通道。我们的微观模型揭示了声子发射过程促进了从 K 谷到其他能量较低的 G 和 的散射事件。双层中的谷。我们结合实验和理论研究明确建立了决定 TMDC 单层和双层中激子量子动力学的不同微观机制。了解激子量子动力学为操纵 TMDC 双层中的自旋谷自由度提供了关键指导。
While valleys (energy extrema) are present in all band structures of solids, their preeminent role in determining exciton resonances and dynamics in atomically thin transition metal dichalcogenides (TMDC) is unique. Using two-dimensional coherent electronic spectroscopy, we find that exciton decoherence occurs on a much faster timescale in MoSe2 bilayers than that in the monolayers. We further identify two population relaxation channels in the bilayer, a coherent and an incoherent one. Our microscopic model reveals that phonon-emission processes facilitate scattering events from the K valley to other lower-energy G and. valleys in the bilayer. Our combined experimental and theoretical studies unequivocally establish different microscopic mechanisms that determine exciton quantum dynamics in TMDC monolayers and bilayers. Understanding exciton quantum dynamics provides critical guidance to the manipulation of spin-valley degrees of freedom in TMDC bilayers.