Ballistic vs. diffusive transport in metals

TL;DR

This paper demonstrates that in metals, ballistic electron transport is weaker than diffusive transport due to rapid femtosecond-scale collisions, with implications for modeling non-thermal electron behavior in nanostructures.

Contribution

It reveals the counterintuitive dominance of diffusive over ballistic transport in metals using the Boltzmann model, linking theory with experimental observations.

Findings

Ballistic transport is weaker than diffusive in metals.

Rapid femtosecond collisions reduce mean-free path.

Modeling of non-thermal electrons is simplified.

Abstract

Using the Boltzmann transport model, we show that, somewhat unintuitively, ballistic transport of electrons in metals is weaker than diffusive transport. This happens because the femtosecond-scale collision rates of the non-thermal electrons makes their mean-free path negligible. Our predictions are correlated with various photoluminescence and nonlinear optics experimental examples both for Continuous Wave (CW) and pulsed illumination, and open the way to easy modelling of the non-thermal electron distributions in metal nanostructures of arbitrary complexity.