2000 character limit reached
Population inversion and ultrafast terahertz nonlinearity of transient Dirac fermions in Cd$_3$As$_2$ (2401.08257v1)
Published 16 Jan 2024 in cond-mat.mtrl-sci, cond-mat.str-el, and physics.optics
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.