Capturing non-equilibrium electron dynamics in metals accurately and efficiently

Abstract

The simulation of non-equilibrium electron distributions is essential for capturing light-metal interactions and therefore the study of photoabsorption, photocatalysis, laser ablation, and many other phenomena. Current methodologies, such as the Boltzmann equation using full collision integrals, describe non-equilibrium electron dynamics in great detail but at often prohibitive computational expense. In contrast, the simplification via a relaxation time approach can hinder the description of important features or, even worse, lead to nonphysical behavior due to the lack of particle and energy conservation. We propose a model that bridges the gap between the Boltzmann equation and two-temperature models to trace non-equilibrium distributions efficiently. This Athermal Electron Model (AthEM) separately captures the dynamics of thermal and athermal electrons and describes the energy and particle flow between two electronic systems and phonons. We show that the results align well with the results of Boltzmann equation and data from photoemission experiments. The AthEM enables the rapid generation of qualitatively accurate non-equilibrium electron distributions and provides a good starting point for further extensions.