Insensitivity of sub-Kelvin electron-phonon coupling to substrate properties

TL;DR

This study investigates how substrate properties affect electron-phonon coupling in Mn-doped Al films below 1 K, finding that coupling strength remains consistent regardless of substrate acoustic differences.

Contribution

The paper demonstrates experimentally that electron-phonon coupling in normal metal films is insensitive to substrate acoustic properties at sub-Kelvin temperatures.

Findings

Electron-phonon coupling constant Sigma is unchanged across different substrates.

Substrate acoustic properties do not significantly influence electron-phonon interactions below 1 K.

Experimental error in measurements is approximately +/- 10%.

Abstract

We have examined the role of the substrate on electron-phonon coupling in normal metal films of Mn-doped Al at temperatures below 1 K. Normal metal-insulator-superconductor junctions were used to measure the electron temperature in the films as a function of Joule heating power and phonon temperature. Theory suggests that the distribution of phonons available for interaction with electrons in metal films may depend on the acoustic properties of the substrate, namely, that the electron-phonon coupling constant Sigma would be larger on the substrate with smaller sound speed. In contrast, our results indicate that within experimental error (typically +/- 10%), Sigma is unchanged among the two acoustically distinct substrates used in our investigation.