Plasmascopy of ultrafast hot charges in solids

TL;DR

This paper introduces a novel electric field-resolved method to observe ultrafast hot charge dynamics in solids, revealing impact ionization and charge trapping phenomena with potential for studying many-body physics.

Contribution

It presents a new approach for real-time measurement of ultrafast charge carrier dynamics in solids using broadband electric field detection.

Findings

First time-resolved observation of impact ionization in germanium

Detection of charge trapping effects at later times

Demonstration of broadband response measurement of photoexcited charges

Abstract

We demonstrate an electric field-resolved approach for probing ultrafast dynamics of photoinjected charges in solids. Direct access to the electric field of few-cycle pulses enables us to measure a broadband response of a medium with associated plasma frequency. We prepare an ensemble of photoinjected hot charge carriers with energies sufficient to trigger impact ionization and establish a framework to measure its dynamics. Our study reveals the first time-resolved observation of the short-lived ultrafast impact ionization in germanium counteracted by trapping of mobile charges at later times. This approach provides a promising route for studying ultrafast many-body physics in photoexcited solids, with predictions from advanced theoretical models.