# Thermalization of hot electrons via interfacial electron-magnon interaction

## TL;DR

This paper investigates a new electron thermalization mechanism in layered superconductor or normal metal structures with ferromagnetic insulators, driven by interfacial electron-magnon interactions, which can dominate heat transfer at low temperatures.

## Contribution

It introduces and analyzes a novel electron thermalization process via interfacial electron-magnon coupling in superconductor/normal metal and ferromagnetic insulator structures.

## Key findings

- Interfacial electron-magnon collisions can dominate heat conductance below certain temperatures.
- Heat conductance is influenced by magnon band gap and induced spin-splitting fields.
- Heat balance measurements can provide insights into magnetic properties beyond magnon spectroscopy.

## Abstract

Recent work on layered structures of superconductors (S) or normal metals (N) in contact with ferromagnetic insulators (FI) has shown how the properties of the previous can be strongly affected by the magnetic proximity effect due to the static FI magnetization. Here we show that such structures can also exhibit a new electron thermalization mechanism due to the coupling of electrons with the dynamic magnetization, i.e., magnons in FI. We here study the heat flow between the two systems and find that in thin films the heat conductance due to the interfacial electron-magnon collisions can dominate over the well-known electron-phonon coupling below a certain characteristic temperature that can be straightforwardly reached with present-day experiments. We also study the role of the magnon band gap and the induced spin-splitting field induced in S on the resulting heat conductance and show that heat balance experiments can reveal information about such quantities in a way quite different from typical magnon spectroscopy experiments.