Entangled magnon-pair generation in a driven synthetic antiferromagnet

TL;DR

This paper demonstrates the spontaneous generation of entangled magnon pairs in a driven synthetic antiferromagnet, revealing quantum effects similar to Hawking radiation and potential for quantum magnonic applications.

Contribution

It introduces a novel mechanism for magnon-pair production driven by spin-orbit torque, with implications for quantum magnonics and energy-efficient spintronic devices.

Findings

Magnon pairs are spontaneously generated under specific conditions.

Magnons are entangled, enabling quantum information applications.

Estimated temperature range for observing these effects.

Abstract

Understanding, manipulating, and using magnons - the quanta of spin waves - for energy-efficient applications is one of the primary goals of magnonics. In this paper, we consider a synthetic antiferromagnet in which one of the ferromagnetic layers is driven by spin-orbit torque. We find that under specific conditions for the magnitude of the spin-orbit torque and field, magnon pairs are spontaneously produced by quantum fluctuations in a way that is similar to Hawking pair production near black-hole horizons. One of the magnons is generated near the interface with the spacer layer in one of the magnetic layers of the synthetic antiferromagnet, while the other magnon is produced in the other magnetic layer. We compute the magnon current due to these spontaneously generated magnon pairs and estimate the temperature below which they should become observable. Additionally, we find that the magnons are entangled, which makes them interesting for future applications in quantum magnonics.