暗激子的微波介电常数电学探测

中文摘要 AI 辅助

原子级薄半导体中的激子几乎总是通过其光学特征来探测，因为人们通常认为这些瞬态准粒子的短寿命排除了电学检测的可能性。在此，我们展示了单层二硫化钨中的光激发激子在千兆赫频率下产生大的、光学可调的介电常数，并且该效应提供了一条无接触的电学途径，用于在纳米尺度上对暗激子进行成像。利用激光照射的微波阻抗显微镜，我们发现高纯度封装薄片表现出与激子光谱共振的纯介电响应，而富含缺陷的样品则由常规光电导主导。扩散的空间映射和亚线性功率依赖性表明长寿命暗激子是主要贡献者，并且激子极化率的第一性原理建模重现了测量的极化率。我们的结果确立了激子作为光学可调介电元件，并引入微波显微镜作为暗激子输运的直接电学探针，分辨率低于100纳米。

英文摘要

Excitons in atomically thin semiconductors are almost always probed through their optical signatures, because the short lifetimes of these transient quasiparticles are generally assumed to preclude electrical detection. Here we show that photoexcited excitons in monolayer tungsten disulfide produce a large, optically tunable permittivity at gigahertz frequencies, and that the effect provides a contact-free electrical route to imaging dark excitons at the nanoscale. Using laser-illuminated microwave impedance microscopy, we find that high-purity encapsulated flakes exhibit a purely dielectric response resonant with the exciton spectrum, whereas defect-rich samples are governed by conventional photoconductivity. Spatial mapping of diffusion and sublinear power dependence identify long-lived dark excitons as the dominant contributors, and first-principles modelling of exciton polarizability reproduces the measured susceptibility. Our results establish excitons as optically tunable dielectric elements and introduce microwave microscopy as a direct electrical probe of dark-exciton transport with sub-100 nm resolution.

发表机构

• University of Texas at Austin（德克萨斯大学奥斯汀分校）
• Washington University in St Louis（华盛顿大学圣路易斯分校）
• University of Wisconsin-Madison（威斯康星大学麦迪逊分校）
• Texas Materials Institute, The University of Texas at Austin（德克萨斯大学奥斯汀分校德克萨斯材料研究所）
• Walker Department of Mechanical Engineering, Materials Science and Engineering Program, University of Texas at Austin（德克萨斯大学奥斯汀分校沃克机械工程系材料科学与工程项目）
• National Institute for Materials Science（日本国立物质材料研究所）

机构由 AI 辅助整理，请以论文原文为准。

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17 pages, 4 figures