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arXiv · 2510.06618

Intrinsic ultrafast edge photocurrent dynamics in WTe$_2$ driven by broken crystal symmetry

Subhashri Chatterjee·Katsumasa Yoshioka·Taro Wakamura·Vasili Perebeinos·Norio Kumada
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Abstract

Directional photocurrents in two-dimensional materials arise from broken crystal symmetry, offering pathways to high-speed, bias-free photodetection beyond conventional devices. Tungsten ditelluride (WTe$_2$), a type-II Weyl semimetal, exhibits robust symmetry-breaking-induced edge photocurrents from competing nonlinear optical and photothermoelectric mechanisms, whose intrinsic dynamics have remained experimentally inaccessible. Here, we directly resolve sub-picosecond edge photocurrent dynamics in WTe$_2$ through ohmic contacts over temperatures from 300 K to 4 K. We demonstrate ultrafast optical-to-electrical conversion with a 3 dB bandwidth of $\sim$250 GHz and reveal picosecond-timescale switching of the net photocurrent direction below 150 K, linked to a Lifshitz transition. This transient bipolar response arises from non-equilibrium Seebeck effects due to asymmetric cooling of hot electrons and holes. These findings reveal previously hidden ultrafast dynamics in symmetry-engineered materials, offering new strategies to disentangle competing photocurrent mechanisms and enabling the development of self-powered, ultrafast optoelectronic devices.

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Subhashri Chatterjee, Katsumasa Yoshioka, Taro Wakamura, Vasili Perebeinos, Norio Kumada. 2025-10-08. Intrinsic ultrafast edge photocurrent dynamics in WTe$_2$ driven by broken crystal symmetry. https://doi.org/10.1021/acs.nanolett.5c04703

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