Distinct terahertz third-harmonic generation of many-body excitonic states

TL;DR

This paper demonstrates the use of terahertz third-harmonic-generation spectroscopy to probe many-body electron-hole states in Cu$_2$O, revealing nonlinear responses related to exciton formation and dissociation at high densities.

Contribution

It introduces a novel experimental approach to study strongly interacting electron-hole states and their nonlinear terahertz responses in semiconductors.

Findings

Efficient terahertz third-harmonic generation linked to excitonic states.

Nonmonotonic nonlinear response dependence on electron-hole density.

Evidence of exciton dissociation at high charge densities.

Abstract

The dynamics of an electron-hole plasma governed by strong Coulomb interaction is a challenging many-body problem.We report on experimental realization of electron-hole many-body states in the picosecond time scale, with tunable densities in a representative semiconductor Cu$_2$O. By using time-resolved optical-pump terahertz third-harmonic-generation spectroscopy, we study the nonlinear terahertz dynamical characteristics of the many-body electron-hole states. We find not only efficient and nonperturbative terahertz third-harmonic yield associated with the excitonic formation, but also a nonmonotonic dependence of the excitonic nonlinear response on the electron-hole density, reflecting the exciton dissociation at high charge density. Our results provide an efficient excitonic sensing of the far-from-equilibrium electron-hole many-body states.