Electron and phonon Cooling in a Superconductor - Normal Metal - Superconductor Tunnel Junction

TL;DR

This paper demonstrates phonon cooling in a superconductor-normal metal-superconductor tunnel junction by analyzing electron and phonon temperatures through current-voltage characteristics and a comprehensive theoretical model.

Contribution

It introduces a quantitative model for phonon cooling that incorporates electron-phonon interactions and Kapitza resistance, enabling precise phonon temperature extraction.

Findings

Normal metal phonons are cooled via electron tunneling.

The model accurately fits experimental data.

Effective phonon temperature can be quantitatively determined.

Abstract

We present evidence for the cooling of normal metal phonons by electron tunneling in a Superconductor - Normal metal - Superconductor tunnel junction. The normal metal electron temperature is extracted by comparing the device current-voltage characteristics to the theoretical prediction. We use a quantitative model for the phonon cooling that includes the electron-phonon coupling in the normal metal and the Kapitza resistance between the substrate and the metal. It gives an excellent fit to the data and enables us to extract an effective phonon temperature in the normal metal.