Dresden 2026 – scientific programme

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DS: Fachverband Dünne Schichten

DS 12: 2D Materials I

DS 12.1: Talk

Wednesday, March 11, 2026, 09:30–09:45, REC/C213

Purcell enhancement of photocurrent in a van der Waals self-cavity — •Xinyu Li — Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

We report the observation of Purcell-enhanced terahertz (THz) photocurrent emission in exfoliated flakes of the van der Waals (vdW) semimetal WTe₂, which act as intrinsic plasmonic self-cavities. Unlike conventional cavities that require external mirrors, micron-scale vdW flakes confine electromagnetic fields via edge reflections, supporting standing-wave plasmonic modes in the THz range. Using ultrafast optoelectronic circuitry, we measured coherent near-field THz emission resulting from nonlinear directional photocurrents excited at crystal edges. Emission spectra reveal resonant enhancement at discrete frequencies, tunable by excitation fluence and device geometry. We attribute this effect to cavity-modified photonic density of states - i.e., the Purcell effect - acting on driven, nonlinear transport currents. An analytical model capturing the self-cavity resonance conditions accurately reproduces experimental trends across multiple devices. Our findings establish WTe₂ as a bias-free, geometry-tunable THz emitter and demonstrate the potential of self-cavity engineering for controlling nonlinear, nonequilibrium dynamics in quantum materials.

Further details are available at arXiv:2507.07987.

Keywords: Ultrafast Phenomena; Terahertz Optoelectronics