Observation of disorder-induced weakening of electron-phonon interaction in thin noble metal films

TL;DR

This study demonstrates that disorder in thin noble metal films causes a T^4 dependence in electron-phonon interactions, weakening electron-lattice coupling at low temperatures, which differs from previously observed power laws.

Contribution

It provides experimental evidence of a T^4 electron-phonon scattering rate in disordered noble metal films, indicating a disorder-mediated coupling mechanism.

Findings

Electron-phonon scattering rate follows a T^4 dependence.

Disorder causes stronger decoupling of electrons from the lattice.

Contrasts with previous T^3 and T^2 power law observations.

Abstract

We have used symmetric normal metal-insulator-superconductor (NIS) tunnel junction pairs, known as SINIS structures, for ultrasensitive thermometry in the temperature range 50 - 700 mK. By Joule heating the electron gas and measuring the electron temperature, we show that the electron-phonon (e-p) scattering rate in the simplest noble metal disordered thin films (Cu,Au) follows a $T^4$ temperature dependence, leading to a stronger decoupling of the electron gas from the lattice at the lowest temperatures. This power law is indicative e-p coupling mediated by vibrating disorder, in contrast to the previously observed $T^3$ and $T^2$ laws.