Twist-angle-dependent interlayer exciton diffusion in WS2-WSe2 heterobilayers
Twist-angle-dependent interlayer exciton diffusion in WS2-WSe2 heterobilayers
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DOI：
10.1038/s41563-020-0670-3
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发表时间：
2020-05-11
期刊：
影响因子：
41.2
通讯作者：
Huang, Libai
中科院分区：
文献类型：
--
作者：
Yuan, Long;Zheng, Biyuan;Huang, Libai
范德华异质结中的层间激子动力学被原子薄层之间的扭角所调制，阐明了莫尔势对激子运动的影响，并为基于二维材料的量子光子器件的设计提供了指导。半导体范德华异质结中莫尔图案引入的纳米周期势已成为设计激子超晶格的平台。然而，我们对激子在莫尔势中运动的理解仍然有限。在这里，我们用暂态吸收显微镜结合第一性原理计算研究了WS2-WSe2异质双层膜中的层间激子动力学和输运。我们发现，在100 meV附近，激子运动受到与扭角相关的莫尔势的调制，并且由于莫尔势和强激子-激子相互作用的相互作用，激子运动偏离了正常扩散。我们的实验结果验证了能量有利的K-Q层间激子的理论预测，并表明激子-布居动力学受K-Q和K-K激子之间扭角相关的能量差控制。这些结果为研究范德华异质结中的激子和自旋输运奠定了基础，对量子通信器件的设计具有重要意义。
Interlayer exciton dynamics in a van der Waals heterostructure is found to be modulated by the twist angle between the atomically thin layers, elucidating the effect of moire potentials on exciton motion and providing guidelines to design quantum photonics devices based on 2D materials.The nanoscale periodic potentials introduced by moire patterns in semiconducting van der Waals heterostructures have emerged as a platform for designing exciton superlattices. However, our understanding of the motion of excitons in moire potentials is still limited. Here we investigated interlayer exciton dynamics and transport in WS2-WSe2 heterobilayers in time, space and momentum domains using transient absorption microscopy combined with first-principles calculations. We found that the exciton motion is modulated by twist-angle-dependent moire potentials around 100 meV and deviates from normal diffusion due to the interplay between the moire potentials and strong exciton-exciton interactions. Our experimental results verified the theoretical prediction of energetically favourable K-Q interlayer excitons and showed exciton-population dynamics that are controlled by the twist-angle-dependent energy difference between the K-Q and K-K excitons. These results form a basis to investigate exciton and spin transport in van der Waals heterostructures, with implications for the design of quantum communication devices.