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arXiv · 2401.08257

Population inversion and ultrafast terahertz nonlinearity of transient Dirac fermions in Cd$_3$As$_2$

Changqing Zhu·Patrick Pilch·Renato M. A. Dantas·Anneke Reinold·Yunkun Yang·Faxian Xiu·Amilcar Bedoya-Pinto·Stuart S. P. Parkin·Roderich Moessner·Zhe Wang
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Abstract

Harmonic generation provides an efficient tool for the study of ultrafast nonlinear dynamics. We report on time-resolved optical-pump terahertz-harmonic-generation spectroscopic investigation of ultrafast nonlinearity in a prototypical three-dimensional Dirac semimetal Cd$_3$As$_2$. A transient population inversion characterized by excessive nonthermal Dirac electrons and holes is found to be very sensitive and responsive to a periodic terahertz drive, leading to very efficient terahertz third-harmonic generation. Based on the Boltzmann transport theory, we analyze the terahertz field-driven kinetics of the transient Dirac fermions that is responsible for the observed strong terahertz nonlinearity.

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Changqing Zhu, Patrick Pilch, Renato M. A. Dantas, Anneke Reinold, Yunkun Yang, Faxian Xiu, Amilcar Bedoya-Pinto, Stuart S. P. Parkin, Roderich Moessner, Zhe Wang. 2024-01-16. Population inversion and ultrafast terahertz nonlinearity of transient Dirac fermions in Cd$_3$As$_2$. https://doi.org/10.1103/physrevb.109.l201111

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