Nonlinear Time Domain Spectroscopy Near a Band Inversion

TL;DR

This paper presents a theoretical study of the nonlinear time domain optical response of Weyl semimetals near band inversion, revealing tunable coherent oscillations driven by ultrafast pulses.

Contribution

It introduces a new theory describing the nonlinear response in Weyl semimetals near band inversion, highlighting a tunable oscillating component at quadratic order.

Findings

Response contains a coherent oscillation proportional to field intensity

Oscillation frequency can be tuned from THz to near IR by chemical potential

Large Berry curvature enhances nonlinear response near band inversion

Abstract

We develop a theory for the nonlinear time domain response of a Weyl semimetal driven by an ultrafast optical pulse. At quadratic order in the driving field we find that the response near a band inversion transition contains a coherent oscillating component proportional field intensity and with a frequency that can be tuned over a wide range (from THz to the near IR) selected by the chemical potential. We illustrate the effect by calculating the induced current as a function of time for a model of a parity broken Weyl semimetal where large Berry curvature near the band inversion transition promotes this nonlinear response.