Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, D-80539, München, Germany.
Department of Physics, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden.
Nat Commun. 2018 Jul 3;9(1):2586. doi: 10.1038/s41467-018-04877-3.
Monolayer transition metal dichalcogenides (TMDs) undergo substantial changes in the single-particle band structure and excitonic optical response upon the addition of just one layer. As opposed to the single-layer limit, the bandgap of bilayer (BL) TMD semiconductors is indirect which results in reduced photoluminescence with richly structured spectra that have eluded a detailed understanding to date. Here, we provide a closed interpretation of cryogenic emission from BL WSe as a representative material for the wider class of TMD semiconductors. By combining theoretical calculations with comprehensive spectroscopy experiments, we identify the crucial role of momentum-indirect excitons for the understanding of BL TMD emission. Our results shed light on the origin of quantum dot formation in BL crystals and will facilitate further advances directed at opto-electronic applications of layered TMD semiconductors in van der Waals heterostructures and devices.
单层过渡金属二卤族化合物（TMDs）在增加一层后，其单粒子能带结构和激子光学响应会发生显著变化。与单层极限不同，双层（BL）TMD 半导体的能带隙是间接的，这导致光致发光减少，且光谱结构丰富，但迄今为止，人们仍难以理解。在这里，我们为 BL WSe 的低温发射提供了一个封闭的解释，WSe 是更广泛的 TMD 半导体类别的代表性材料。通过将理论计算与全面的光谱实验相结合，我们确定了动量间接激子在理解 BL TMD 发射中的关键作用。我们的研究结果揭示了 BL 晶体中量子点形成的起源，并将促进进一步的进展，以实现层状 TMD 半导体在范德华异质结构和器件中的光电应用。
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