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Excitonic Effect Drives Ultrafast Dynamics in van der Waals Heterostructures

机译:激发器效果在van der Waals异质结构中推动超快动态

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Recent experiments revealed stacking-configuration-independent and ultrafast charge transfer in transition metal dichalcogenides van der Waals (vdW) heterostructures, which is surprising given strong exciton binding energies and large momentum mismatch across the heterojunctions. Previous theories failed to provide a comprehensive physical picture for the charge transfer mechanisms. To address this challenge, we developed a first-principles framework which can capture exciton-phonon interaction in extended systems. We find that excitonic effect does not impede, but actually drives ultrafast charge transfer in vdW heterostructures. The many-body electron-hole interaction affords cooperation among the electrons, which relaxes the constraint on momentum conservation and reduces energy gaps for charge transfer. We uncover a two-step process in exciton dynamics: ultrafast hole transfer followed by much longer relaxation of intermediate "hot" excitons. This work establishes that many-body excitonic effect is crucial to the ultrafast dynamics and provides a basis to understand relevant phenomena in vdW heterostructures.
机译:最近的实验揭示了堆叠结构无关的和超快电荷转移在过渡金属二甲基化物van der Waals(VDW)异质结构中,令人惊讶的是,赋予杂交功能的强大动量混合。以前的理论未能为电荷转移机制提供全面的物理图片。为了解决这一挑战,我们开发了一个第一原理框架,可以在扩展系统中捕获exiton-phonon交互。我们发现激发器效果不妨碍,但实际上驱动VDW异质结构中的超快电荷转移。许多身体电子空穴相互作用提供电子之间的合作,这在动力节省和降低电荷转移的能量间隙上放宽了对电量的约束。我们在Exciton Dynamics中揭示了两步过程:超快孔转移,然后更长的中间“热”激子放松。这项工作确定了许多身体兴趣效果对超快动态至关重要,并为理解VDW异质结构中的相关现象提供了基础。

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