Phonon Amplification via Magnetoelastic Klein Scattering

TL;DR

This paper proposes a novel setup using magnetoelastic Klein scattering to amplify phonons by exploiting negative-energy magnons in a ferromagnetic insulator, potentially enhancing phonon lifetimes for future nanoscale devices.

Contribution

It introduces a new phonon amplification mechanism based on magnetoelastic Klein scattering involving negative-energy magnons in a ferromagnetic insulator.

Findings

Phonon amplitude can be increased via interaction with negative-energy magnons.

The setup demonstrates a method to potentially extend phonon lifetimes.

Magnetoelastic Klein scattering enables energy transfer that amplifies phononic signals.

Abstract

Materials exhibit various wave-like excitations, among which phonons (lattice vibrations) and magnons (oscillations in ferromagnetic ordering) hold significant promise for future nanoscale technologies. Exploring the interaction between these excitations may pave the way for innovative devices that leverage their complementary strengths. This article presents a set-up designed to amplify an incoming phononic current, potentially enhancing the phonon lifetime. The set-up consists of a nonmagnetic and ferromagnetic insulator. The ferromagnet is polarized opposite to the external magnetic field with spin-orbit torque, which allows for negative-energy magnons. Phonons that are incoming from the nonmagnetic side will interact with the negative-energy magnons via magnetoelastic coupling. The reflected phonon will increase in amplitude as a result of energy conservation. This interaction between negative-energy magnons and phonons is an example of Klein scattering. This work opens new avenues for the development of advanced devices that capitalize on the combined properties of phonons and magnons.