Quasiparticle Trapping In Three Terminal Ferromagnetic Tunneling Devices

TL;DR

This paper demonstrates how ferromagnetic nano-volumes can trap quasiparticles in superconductor/ferromagnet structures, leading to localized heating and potential control of out-of-equilibrium superconductivity.

Contribution

It introduces a method to trap quasiparticles in ferromagnetic regions, revealing new ways to manipulate superconducting states out of equilibrium.

Findings

Quasiparticles are effectively trapped in ferromagnetic nano-volumes.

Electronic temperature in the trap can be increased by up to 60%.

Proximity effect is suppressed in ferromagnetic regions.

Abstract

Hybrid Superconductor/Ferromagnet structures have been investigated recently to address the interplay between ferromagnetism and superconductivity. They also open up new routes for the investigation of out of equilibrium superconductivity. Here, we show how it is possible for out of equilibrium excitations produced in a superconducting thin film (S) to be localized in a ferromagnetic trap (F). Specifically, a ferromagnetic nano-volume in good contact with S represents a potential well for the quasiparticles (QPs) at the gap edge. As the superconducting proximity effect is highly suppressed in F, QPs get efficiently trapped and they share their energy with the free electrons in the trap. The electronic temperature Te in the trap can be increased by up to 60% from the bath temperature at 320 mK as measured by tunneling spectroscopy using a second junction.