AI 中文总结
该研究探究低温下应变封装hBN的WSe2单层的激子动力学，发现拉伸应变加速瞬态激子扩散，压缩应变可周期性调制其扩散，揭示应变可调控二维半导体的瞬态光致发光与激子扩散。
AI 中文摘要
钨基过渡金属二硫化物具有暗激子作为能量最低态，这些态对激子热化和传播至关重要，且通过显著声子边带主导低温光致发光。共振激发后会形成高迁移率的热暗激子，其迅速热化至平衡分布。应变会改变激子能量势垒，尤其是亮激子与暗激子态的相对能量差。应变对非平衡激子的瞬态光致发光及扩散的影响迄今仍未被充分探究。本工作研究低温下应变封装于hBN的WSe2单层中的时空激子动力学，证明拉伸应变会急剧增加热激子的过剩能量，从而加速其瞬态扩散，这可归因于亮激子到暗激子的声子介导散射被抑制。此外，我们预测在压缩应变下，由应变驱动的M声子发射会导致瞬态激子扩散的周期性调制。获得的微观见解表明，应变可用于调控具有技术应用前景的二维半导体中的瞬态光致发光和激子扩散。
英文摘要
Tungsten-based transition metal dichalcogenides exhibit dark excitons as the energetically lowest states. These are crucial for exciton thermalization and propagation and they dominate low-temperature photoluminescence via the emergence of pronounced phonon sidebands. After a resonant excitation, highly mobile hot dark excitons are formed, which quickly thermalize into an equilibrium distribution. The application of strain modifies the exciton energy landscape and, in particular, the relative energy separation between bright and dark exciton states. The impact of strain on the transient photoluminescence and diffusion of non-equilibrium excitons has remained largely unexplored so far. In this work, we investigate the spatiotemporal exciton dynamics in strained hBN-encapsulated WSe2 monolayers at cryogenic temperatures. We demonstrate that tensile strain abruptly increases the excess energy of hot excitons, thereby accelerating their transient diffusion. We trace this back to suppressed phonon-mediated scattering from bright to dark excitons. Furthermore, we predict a periodic modulation of the transient exciton diffusion in the presence of a compressive strain resulting from strain-driven emission of M phonons. The gained microscopic insights illustrate how strain can be used to engineer transient photoluminescence and exciton diffusion in technologically promising 2D semiconductors.
Comments8 pages, 4 figures, Supplementary Material
