标题： 范德瓦尔斯等离子体自腔中光电流的 Purcell 增强 显示英文标题

标题： Purcell enhancement of photogalvanic currents in a van der Waals plasmonic self-cavity

摘要： 腔体提供了一种方法，通过在特定频率和动量处选择性增强光-物质相互作用，来操控量子材料的光学和电子响应。 虽然腔体通常涉及外部结构，但范德华（vdW）材料的剥离薄片由于其小的有限尺寸，可以形成内在的自腔体，将电磁场限制在等离激元腔模式中，其特征是驻波电流分布。 虽然在光学频率下对腔增强现象已有深入研究，但自腔体对非线性电子响应（如光电流）的影响在太赫兹范围内仍大多未被探索，而太赫兹范围对于新兴的超快光电子技术至关重要。 在此，我们报告了在vdW半金属WTe$_2$中由自腔体引起的光电流的Purcell增强。 使用超快光电子电路，我们测量了在样品边缘激发的非线性光电流导致的相干近场太赫兹辐射。 我们观察到在有限频率下的增强辐射，其可通过激发通量和样品几何结构进行调节，这归因于由腔边界控制的等离激元干涉效应。 我们开发了一种解析理论，能够捕捉多个器件中的腔共振条件和光谱响应。 我们的发现确立了WTe$_2$作为无偏置、几何可调的太赫兹发射器，并展示了自腔体工程在控制量子材料中非平衡动力学方面的潜力。 显示英文摘要

摘要： Cavities provide a means to manipulate the optical and electronic responses of quantum materials by selectively enhancing light-matter interaction at specific frequencies and momenta. While cavities typically involve external structures, exfoliated flakes of van der Waals (vdW) materials can form intrinsic self-cavities due to their small finite dimensions, confining electromagnetic fields into plasmonic cavity modes, characterized by standing-wave current distributions. While cavity-enhanced phenomena are well-studied at optical frequencies, the impact of self-cavities on nonlinear electronic responses--such as photogalvanic currents--remains largely unexplored, particularly in the terahertz regime, critical for emerging ultrafast optoelectronic technologies. Here, we report a self-cavity-induced Purcell enhancement of photogalvanic currents in the vdW semimetal WTe$_2$. Using ultrafast optoelectronic circuitry, we measured coherent near-field THz emission resulting from nonlinear photocurrents excited at the sample edges. We observed enhanced emission at finite frequencies, tunable via excitation fluence and sample geometry, which we attribute to plasmonic interference effects controlled by the cavity boundaries. We developed an analytical theory that captures the cavity resonance conditions and spectral response across multiple devices. Our findings establish WTe$_2$ as a bias-free, geometry-tunable THz emitter and demonstrate the potential of self-cavity engineering for controlling nonlinear, nonequilibrium dynamics in quantum materials.