墨西哥帽拓扑半导体的中红外-太赫兹巨光子响应
Giant Photonic Response of Mexican-hat Topological Semiconductors for Mid-infrared to THz Applications
摘要：
中红外（MIR）、远红外（FIR）到太赫兹（THz）频率是电磁波谱中应用最少的部分。传统的半导体技术如激光二极管和光电探测器在可见光范围内是成功的，但是当扩展到MIR/FIR/THz范围时仍然面临巨大的挑战。在本文中，我们表明，拓扑绝缘体（TI），特别是那些与墨西哥帽能带结构（MHBS），提供了一条路线，以克服这些挑战。MHBS TI的光学响应可以比正常半导体在光学跃迁边缘处的光学响应大一到两个数量级。我们探索了拓扑材料的数据库，发现了一些MHBS TI的带隙位于$0.05\sim 0.5~\rm eV$之间，并在过渡边缘具有$10^4 \sim 10^5~\rm cm^{-1}$量级的巨大增益（吸收系数）。这些发现可能会大大推动潜在的MIR/FIR/THz应用，如光子源，探测器，超快电光器件和量子信息技术。
英文摘要：
The mid-infrared (MIR), far-infrared (FIR) to terahertz (THz) frequencies are the least developed parts of the electromagnetic spectrum for applications. Traditional semiconductor technologies like laser diodes and photodetectors are successful in the visible light range, but are still confronted with great challenges when extended into the MIR/FIR/THz range. In this paper, we demonstrate that topological insulators (TIs), especially those with Mexican-hat band structure (MHBS), provide a route to overcome these challenges. The optical responses of MHBS TIs can be one to two orders of magnitude larger than that of normal semiconductors at the optical-transition edge. We explore the databases of topological materials and discover a number of MHBS TIs whose bandgaps lie between $0.05\sim 0.5~\rm eV$ and possess giant gains (absorption coefficients) on the order of $10^4 \sim 10^5~\rm cm^{-1}$ at the transition edge. These findings may significantly boost potential MIR/FIR/THz applications such as photon sources, detectors, ultrafast electro-optical devices, and quantum information technologies.
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