DOE OSTI · 2917453
Purcell enhancement of directional edge photocurrent in a van der Waals self-cavity
Abstract
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 directional photocurrent—remains largely unexplored, particularly in the terahertz regime, critical for emerging ultrafast optoelectronic technologies. Here, we report a self-cavity-induced Purcell enhancement of directional photocurrents 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.
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Li, Xinyu [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany)] (ORCID:0000000343456270), Hagelstein, Jesse [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany)], Kipp, Gunda [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany)] (ORCID:0009000717203700), Sturm, Felix [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0009000689886099), Kusyak, Kateryna [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0009000341159034), Huang, Yunfei [Columbia Univ., New York, NY (United States)], Schulte, Benedikt [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0000000176050547), Potts, Alexander M. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0000000335021701), Stensberg, Jonathan [Columbia Univ., New York, NY (United States)] (ORCID:0000000176053553), Quirós-Cordero, Victoria [Columbia Univ., New York, NY (United States)], Trovatello, Chiara [Columbia Univ., New York, NY (United States); Politecnico di Milano (Italy)] (ORCID:0000000281509743), Peng, Zhi Hao [Columbia Univ., New York, NY (United States)], Hu, Chaowei [Univ. of Washington, Seattle, WA (United States)] (ORCID:0000000320710109), DeStefano, Jonathan M. [Univ. of Washington, Seattle, WA (United States)] (ORCID:0000000272201261), Fechner, Michael [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany)] (ORCID:0000000327747684), Taniguchi, Takashi [National Institute for Materials Science (NIMS), Tsukuba (Japan)] (ORCID:0000000214673105), Watanabe, Kenji (ORCID:0000000337018119), Schuck, P. James [Columbia Univ., New York, NY (United States)] (ORCID:0000000192442671), Xu, Xiaodong [Columbia Univ., New York, NY (United States); Univ. of Washington, Seattle, WA (United States)] (ORCID:0000000303482095), Chu, Jiun-Haw [Univ. of Washington, Seattle, WA (United States)] (ORCID:0000000162221210), Zhu, Xiaoyang (ORCID:0000000220908484), Rubio, Angel [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Flatiron Institute, New York, NY (United States). Simons Foundation] (ORCID:0000000320603151), Michael, Marios H. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany)], Day, Matthew W. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)], Bretscher, Hope M. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0000000165514721), McIver, James W. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Center for Free-Electron Laser Science, Hamburg (Germany); Columbia Univ., New York, NY (United States)] (ORCID:0000000301825031). 2026-04-28. Purcell enhancement of directional edge photocurrent in a van der Waals self-cavity. https://doi.org/10.1038/s41467-026-72260-8
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