Li Wei-Hua, Lin Jhen-Dong, Lo Ping-Yuan, Peng Guan-Hao, Hei Ching-Yu, Chen Shao-Yu, Cheng Shun-Jen
Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
Center of Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan.
Nanomaterials (Basel). 2023 May 26;13(11):1739. doi: 10.3390/nano13111739.
In this work, we present a comprehensive theoretical and computational investigation of exciton fine structures of WSe2-monolayers, one of the best-known two-dimensional (2D) transition-metal dichalcogenides (TMDs), in various dielectric-layered environments by solving the first-principles-based Bethe-Salpeter equation. While the physical and electronic properties of atomically thin nanomaterials are normally sensitive to the variation of the surrounding environment, our studies reveal that the influence of the dielectric environment on the exciton fine structures of TMD-MLs is surprisingly limited. We point out that the non-locality of Coulomb screening plays a key role in suppressing the dielectric environment factor and drastically shrinking the fine structure splittings between bright exciton (BX) states and various dark-exciton (DX) states of TMD-MLs. The intriguing non-locality of screening in 2D materials can be manifested by the measurable non-linear correlation between the BX-DX splittings and exciton-binding energies by varying the surrounding dielectric environments. The revealed environment-insensitive exciton fine structures of TMD-ML suggest the robustness of prospective dark-exciton-based optoelectronics against the inevitable variation of the inhomogeneous dielectric environment.
在这项工作中，我们通过求解基于第一性原理的贝特 - 萨尔皮特方程，对WSe₂单层（最著名的二维（2D）过渡金属二硫属化物（TMDs）之一）在各种介电层环境中的激子精细结构进行了全面的理论和计算研究。虽然原子级薄的纳米材料的物理和电子性质通常对周围环境的变化敏感，但我们的研究表明，介电环境对TMD单层激子精细结构的影响出奇地有限。我们指出，库仑屏蔽的非局域性在抑制介电环境因素以及大幅缩小TMD单层明亮激子（BX）态和各种暗激子（DX）态之间的精细结构分裂方面起着关键作用。通过改变周围介电环境，二维材料中有趣的屏蔽非局域性可以通过BX - DX分裂与激子结合能之间可测量的非线性相关性表现出来。所揭示的TMD单层对环境不敏感的激子精细结构表明，基于暗激子的前瞻性光电器件对于不均匀介电环境不可避免的变化具有鲁棒性。
