Hot electrons in low-dimensional phonon systems

TL;DR

This paper demonstrates that the standard bulk electron-phonon coupling model fails to accurately describe low-temperature behavior in low-dimensional phonon systems, revealing a crossover to a different temperature dependence and indicating widespread model breakdown.

Contribution

The study applies an exact model to semi-infinite substrates, showing the standard model's predictions are coincidental and identifying a new temperature scaling at low temperatures.

Findings

Standard model predicts a T^6 log T scaling at low temperatures.

Experimental data suggest the standard model often fails in low-dimensional systems.

A crossover from T^5 to T^6 log T behavior is identified.

Abstract

A simple bulk model of electron-phonon coupling in metals has been surprisingly successful in explaining experiments on metal films that actually involve surface- or other low-dimensional phonons. However, by an exact application of this standard model to a semi-infinite substrate with a free surface, making use of the actual vibrational modes of the substrate, we show that such agreement is fortuitous, and that the model actually predicts a low-temperature crossover from the familiar T^5 temperature dependence to a stronger T^6 log T scaling. Comparison with existing experiments suggests a widespread breakdown of the standard model of electron-phonon thermalization in metals.