# Terahertz third-harmonic generation of lightwave driven Weyl fermions far from equilibrium

Source: [Terahertz third-harmonic generation of lightwave driven Weyl fermions far from equilibrium](<https://www.sota2.com/research/paper/68fa4b741e209131ce946206>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-11-27T05:01:19.526Z

Authors: Patrick Pilch, Changqing Zhu, Sergey Kovalev, Renato M. A. Dantas, Amilcar Bedoya-Pinto, Stuart S. P. Parkin, Zhe Wang

Published: 2025-08-22T07:42:10.000Z

## Abstract

We report on time-resolved ultrafast terahertz third-harmonic generation spectroscopy of nonequilibrium dynamics of Weyl fermions in a nanometer thin film of the Weyl semimetal TaP. Terahertz third-harmonic generation is observed at room temperature under the drive of a multicycle narrowband terahertz pulse with a peak field strength of down to tens of kV/cm. The observed terahertz third-harmonic generation exhibits a perturbative cubic power-law dependence on the terahertz drive. By varying the polarization of the drive pulse from linear to elliptical, we realize a sensitive tuning of the third harmonic yield. By carrying out theoretical analysis based on the Boltzmann transport theory, we can properly describe the experimental results and ascribe the observed THz nonlinearity to field-driven kinetics of the Weyl fermions.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2508.16166>)

[PDF](<https://arxiv.org/pdf/2508.16166.pdf>)