Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures
Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures
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DOI：
10.1038/s41567-018-0123-y
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发表时间：
2018-08-01
期刊：
影响因子：
19.6
通讯作者：
Korn, Tobias
中科院分区：
文献类型：
--
作者：
Kunstmann, Jens;Mooshammer, Fabian;Korn, Tobias
过渡金属二硫族化合物的单层具有特殊的光学性质，由紧密结合的电子-空穴对（称为激子）主导。通过确定地堆叠单个单层来创建范德华异质结构可以通过选择材料(1)和层的相对方向（2,3）来调整各种特性。在这些结构中，出现了一种新型激子，其中电子和空穴在空间上被分隔成不同的层。这些层间激子（4-6）允许探索多体量子现象（7,8），并且非常适合谷电子应用(9)。由单层布里渊带的K谷产生的完全空间分离的电子和空穴的基本模型通常用于描述这类激子。在这里，我们结合光致发光光谱和第一性原理计算来扩展层间激子的概念。我们在MoS2/WSe2异质结构中发现了一个部分电荷分离的电子-空穴对，其中空穴位于伽玛点，电子位于K谷。我们通过改变层的相对取向来控制这种新型动量空间间接强束缚激子的发射能量。这些发现是理解和控制范德华异质结构和器件中激子效应的关键一步。
Monolayers of transition-metal dichalcogenides feature exceptional optical properties that are dominated by tightly bound electron-hole pairs, called excitons. Creating van der Waals heterostructures by deterministically stacking individual monolayers can tune various properties via the choice of materials(1) and the relative orientation of the layers(2,3). In these structures, a new type of exciton emerges where the electron and hole are spatially separated into different layers. These interlayer excitons(4-6) allow exploration of many-body quantum phenomena(7,8) and are ideally suited for valleytronic applications(9). A basic model of a fully spatially separated electron and hole stemming from the K valleys of the monolayer Brillouin zones is usually applied to describe such excitons. Here, we combine photoluminescence spectroscopy and first-principles calculations to expand the concept of interlayer excitons. We identify a partially charge-separated electron-hole pair in MoS2/WSe2 heterostructures where the hole resides at the Gamma point and the electron is located in a K valley. We control the emission energy of this new type of momentum-space indirect, yet strongly bound exciton by variation of the relative orientation of the layers. These findings represent a crucial step towards the understanding and control of excitonic effects in van der Waals heterostructures and devices.