Charge dynamics electron microscopy: nanoscale imaging of femtosecond plasma dynamics

TL;DR

This paper introduces charge dynamics electron microscopy (CDEM), a novel ultrafast imaging technique that captures nanoscale electron cloud evolution on femtosecond timescales, revealing microscopic mechanisms of plasma dynamics in metals.

Contribution

The study develops and demonstrates CDEM, enabling simultaneous nanometer and femtosecond resolution imaging of electron cloud dynamics, advancing understanding of non-equilibrium plasma phenomena.

Findings

Revealed microscopic mechanisms of electron emission and screening.

Achieved nanometer and femtosecond resolution in charge dynamics imaging.

Provided insights into collective electron cloud behavior.

Abstract

Understanding and actively controlling the spatio-temporal dynamics of non-equilibrium electron clouds is fundamental for the design of light and electron sources, novel high-power electronic devices, and plasma-based applications. However, electron clouds evolve in a complex collective fashion on nanometer and femtosecond scales, producing electromagnetic screening that renders them inaccessible to existing optical probes. Here, we solve the long-standing challenge of characterizing the evolution of electron clouds generated upon irradiation of metallic structures using an ultrafast transmission electron microscope to record the charged plasma dynamics. Our approach to charge dynamics electron microscopy (CDEM) is based on the simultaneous detection of electron-beam acceleration and broadening with nanometer/femtosecond resolution. By combining experimental results with comprehensive microscopic theory, we provide deep understanding of this highly out-of-equilibrium regime, including previously inaccessible intricate microscopic mechanisms of electron emission, screening by the metal, and collective cloud dynamics. Beyond the present specific demonstration, the here introduced CDEM technique grants us access to a wide range of non-equilibrium electrodynamic phenomena involving the ultrafast evolution of bound and free charges on the nanoscale.