Lo Tsz Wing, Chen Xiaolin, Zhang Zhedong, Zhang Qiang, Leung Chi Wah, Zayats Anatoly V, Lei Dangyuan
Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong S.A.R.
Department of Applied Physics, The Hong Kong Polytechnic University, 11 Yuk Choi Road, Hung Hom, Hong Kong S.A.R.
Nano Lett. 2022 Mar 9;22(5):1915-1921. doi: 10.1021/acs.nanolett.1c04360. Epub 2022 Feb 28.
Spin-forbidden excitons in monolayer transition metal dichalcogenides are optically inactive at room temperature. Probing and manipulating these dark excitons are essential for understanding exciton spin relaxation and valley coherence of these 2D materials. Here, we show that the coupling of dark excitons to a metal nanoparticle-on-mirror cavity leads to plasmon-induced resonant emission with the intensity comparable to that of the spin-allowed bright excitons. A three-state quantum model combined with full-wave electrodynamic calculations reveals that the radiative decay rate of the dark excitons can be enhanced by nearly 6 orders of magnitude through the Purcell effect, therefore compensating its intrinsic nature of weak radiation. Our nanocavity approach provides a useful paradigm for understanding the room-temperature dynamics of dark excitons, potentially paving the road for employing dark exciton in quantum computing and nanoscale optoelectronics.
单层过渡金属二硫属化物中的自旋禁戒激子在室温下是光学非活性的。探测和操纵这些暗激子对于理解这些二维材料的激子自旋弛豫和谷相干至关重要。在这里，我们表明暗激子与镜上金属纳米颗粒腔的耦合导致等离子体诱导的共振发射，其强度与自旋允许的亮激子相当。一个三态量子模型与全波电动力学计算相结合表明，通过珀塞尔效应，暗激子的辐射衰减率可以提高近6个数量级，从而补偿其固有的弱辐射特性。我们的纳米腔方法为理解暗激子的室温动力学提供了一个有用的范例，有可能为在量子计算和纳米级光电子学中应用暗激子铺平道路。
