Enhanced magnon spin current using the bosonic Klein paradox

TL;DR

This paper proposes a method to amplify magnon spin currents in magnetic nanostructures by exploiting the bosonic Klein paradox, enabling potential magnon amplifier devices and advancing the study of relativistic bosonic particles.

Contribution

It introduces a novel approach to stabilize magnons and antimagnons via spin-orbit torques, leading to current amplification through the bosonic Klein paradox in magnetic systems.

Findings

Magnon reflection coefficient can exceed one, indicating amplification.

Stabilization of antimagnons through tuning dissipation.

Potential for developing magnon amplifiers for spintronics.

Abstract

Efficient manipulation of magnons for information processing is a central topic in spintronics and magnonics. An outstanding challenge for long-distance spin transport with minimal dissipation is to overcome the relaxation of magnons and to amplify the spin current they carry. Here, we propose to amplify magnon currents based on the realization of the bosonic Klein paradox in magnetic nanostructures. This paradox involves the magnon's antiparticle, the antimagnon, of which the existence is usually precluded by magnetic instabilities as it is an excitation at negative energy. We show that, by appropriately tuning the effective dissipation through spin-orbit torques, both magnons and antimagnons are dynamically stabilized. As a result, we find that the reflection coefficient of incident magnons at an interface between two coupled magnets can become larger than one, thereby amplifying the reflected magnon current. Our findings can lead to magnon amplifier devices for spintronic applications. Furthermore, our findings yield a solid-state platform to study the relativistic behavior of bosonic particles, which is an outstanding challenge with fundamental particles.