Generating and detecting radiation in the technologically relevant range of the so-called terahertz gap (0.1–10 THz) is challenging because of a lack of efficient sources and detectors. Quantum dots in carbon nanotubes have shown great potential to build sensitive terahertz detectors, usually based on photon-assisted tunneling. A recently reported mechanism combining resonant quantum dot transitions and tunneling barrier asymmetries results in a narrow linewidth photocurrent response with a large signal-to-noise ratio under weak THz radiation. That device was sensitive to one frequency, corresponding to transitions between equidistant quantized states. In this work we show, using numerical simulations together with scanning tunneling spectroscopy studies of a defect-induced metallic zigzag single-walled carbon nanotube quantum dot, that breaking simultaneously various symmetries in metallic nanotube quantum dots of arbitrary chirality strongly relaxes the selection rules in the electric dipole approximation and removes energy degeneracies. This leads to a richer set of allowed optical transitions spanning frequencies from 1 THz to several tens of THz, for a ∼10 nm quantum dot. Based on these findings, we propose a terahertz detector device based on a metallic single-walled carbon nanotube quantum dot defined by artificial defects. Depending on its length and contacts transparency, the operating regimes range from a high-resolution gate-tunable terahertz sensor to a broadband terahertz detector. Our calculations indicate that the device is largely unaffected by temperatures up to 100 K, making carbon nanotube quantum dots with broken symmetries a promising platform to design tunable terahertz detectors that could operate at liquid nitrogen temperatures.

中文翻译：

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具有破坏对称性的金属碳纳米管量子点作为可调谐太赫兹检测平台

由于缺乏有效的源和检测器，在所谓的太赫兹间隙（0.1-10 THz）的技术相关范围内产生和检测辐射具有挑战性。碳纳米管中的量子点已显示出构建灵敏的太赫兹探测器的巨大潜力，通常基于光子辅助隧道效应。最近报道的一种结合共振量子点跃迁和隧道势垒不对称性的机制导致窄线宽光电流响应在弱太赫兹辐射下具有大信噪比。该设备对一个频率敏感，对应于等距量化状态之间的转换。在这项工作中，我们展示了使用数值模拟和扫描隧道光谱研究缺陷诱导的金属锯齿形单壁碳纳米管量子点，同时打破任意手性的金属纳米管量子点中的各种对称性强烈放宽了电偶极子近似中的选择规则并消除了能量简并。这导致了一组更丰富的允许的光学跃迁，频率范围从 1 THz 到几十 THz，对于约 10 nm 量子点。基于这些发现，我们提出了一种基于人工缺陷定义的金属单壁碳纳米管量子点的太赫兹探测器装置。根据其长度和接触透明度，操作范围从高分辨率门可调谐太赫兹传感器到宽带太赫兹探测器。我们的计算表明，该设备在很大程度上不受高达 100 K 的温度的影响，