Hot electrons in magnetic point contacts as a photon source

TL;DR

This paper proposes using ferromagnetic-normal metal point contacts to generate tunable microwave photons via hot electron spin relaxation, demonstrating stimulated emission and suggesting new spin-based laser technologies.

Contribution

It introduces a novel application of point contacts as a tunable microwave photon source through spin-flip relaxation of hot electrons.

Findings

Detection of photon emission via transport spectroscopy

Demonstration of stimulated emission in 10-100 GHz range

Potential for spin-injection based metal lasers

Abstract

We propose to use a point contact between a ferromagnetic and a normal metal in the presence of a magnetic field for creating a large inverted spin-population of hot electrons in the contact core. The key point of the proposal is that when these hot electrons relax by flipping their spin, microwave photons are emitted, with a frequency tunable by the applied magnetic field. While point contacts is an established technology their use as a photon source is a new and potentially very useful application. We show that this photon emission process can be detected by means of transport spectroscopy and demonstrate stimulated emission of radiation in the 10-100 GHz range for a model point contact system using a minority-spin ferromagnetic injector. These results can potentially lead to new types of lasers based on spin injection in metals.