Structure of the moire exciton captured by imaging its electron and hole
Structure of the moire exciton captured by imaging its electron and hole
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DOI：
10.1038/s41586-021-04360-y
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发表时间：
2022-03-10
期刊：
影响因子：
64.8
通讯作者：
Dani, Keshav M.
中科院分区：
文献类型：
--
作者：
Karni, Ouri;Barre, Elyse;Dani, Keshav M.
层间激子（ILX）-电子-空穴对结合在两个原子级薄的层状半导体上-已经成为研究激子凝聚（1-4），单光子发射和其他量子信息应用（5-7）的有吸引力的平台。然而，尽管进行了广泛的光学光谱研究（8-12），关于它们的大小，谷结构和莫尔电位的影响的关键信息仍然未知。在这里，在WSe 2/MoS 2异质结构中，我们捕获了结合形成ILX的两种粒子的时间分辨和动量分辨分布的图像：电子和空穴。因此，我们获得了ILX直径约5.2 nm的直接测量，与莫尔晶胞长度6.1 nm相当，以及其质心的定位。令人惊讶的是，这个大ILX被发现钉扎到一个区域内的莫尔细胞的直径只有1.8纳米，小于激子本身的大小。ILX的这种高度局部化得到Bethe-Salpeter方程计算的支持，并证明ILX可以局部化在小的莫尔晶胞内。与大型莫尔细胞不同，这些在大区域上是均匀的，允许形成用于量子技术的局部激发的扩展阵列。
Interlayer excitons (ILXs) - electron-hole pairs bound across two atomically thin layered semiconductors - have emerged as attractive platforms to study exciton condensation(1-4), single-photon emission and other quantum information applications(5-7). Yet, despite extensive optical spectroscopic investigations(8-12), critical information about their size, valley configuration and the influence of the moire potential remains unknown. Here, in a WSe2/MoS2 heterostructure, we captured images of the time-resolved and momentum-resolved distribution of both of the particles that bind to form the ILX: the electron and the hole. We thereby obtain a direct measurement of both the ILX diameter of around 5.2 nm, comparable with the moire-unit-cell length of 6.1 nm, and the localization of its centre of mass. Surprisingly, this large ILX is found pinned to a region of only 1.8 nm diameter within the moire cell, smaller than the size of the exciton itself. This high degree of localization of the ILX is backed by Bethe-Salpeter equation calculations and demonstrates that the ILX can be localized within small moire unit cells. Unlike large moire cells, these are uniform over large regions, allowing the formation of extended arrays of localized excitations for quantum technology.