Vertically stacked transition metal dichalcogenide-graphene heterostructures provide a platform for novel optoelectronic applications with high photoresponse speeds. Photoinduced nonequilibrium carrier and lattice dynamics in such heterostructures underlie these applications but have not been understood. In particular, the dependence of these photoresponses on the twist angle, a key tuning parameter, remains elusive. Here, using ultrafast electron diffraction, we report the simultaneous visualization of charge transfer and electron–phonon coupling in MoS₂-graphene heterostructures with different stacking configurations. We find that the charge transfer timescale from MoS₂ to graphene varies strongly with twist angle, becoming faster for smaller twist angles, and show that the relaxation timescale is significantly shorter in a heterostructure as compared to a monolayer. These findings illustrate that twist angle constitutes an additional tuning knob for interlayer charge transfer in heterobilayers and deepen our understanding of fundamental photophysical processes in heterostructures, of importance for future applications in optoelectronics and light harvesting.

中文翻译：

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MoS2-石墨烯范德华异质结构中的扭转角相关超快电荷转移

垂直堆叠的过渡金属二硫属化物-石墨烯异质结构为具有高光响应速度的新型光电应用提供了平台。这种异质结构中的光致非平衡载流子和晶格动力学是这些应用的基础，但尚未被理解。特别是，这些光响应对关键调谐参数扭转角的依赖性仍然难以捉摸。在这里，我们使用超快电子衍射，报告了具有不同堆叠配置的MoS _{2 -}石墨烯异质结构中电荷转移和电子-声子耦合的同时可视化。我们发现 MoS ₂的电荷转移时间尺度石墨烯的石墨烯随扭转角变化很大，对于较小的扭转角变得更快，并且表明与单层相比，异质结构中的弛豫时间尺度明显更短。这些发现表明，扭转角构成了异质双层中层间电荷转移的额外调节旋钮，并加深了我们对异质结构中基本光物理过程的理解，这对未来光电子学和光收集的应用具有重要意义。