Optomagnonic Josephson effect in antiferromagnets

TL;DR

This paper proposes a novel ultrafast spin transport method in antiferromagnets using optomagnonic Bose-Einstein condensates induced by the optical Barnett effect, leading to a Josephson effect with picosecond oscillation periods.

Contribution

It introduces the concept of an optomagnonic Josephson effect in antiferromagnets, leveraging optical magnon BECs for ultrafast spin transport, a new approach in spintronics.

Findings

Optical Barnett effect induces magnon BECs in antiferromagnets.

Coherent optical magnons generate a Josephson spin current.

Ultrafast oscillation period of the Josephson effect in the picosecond range.

Abstract

Combining advanced technologies of optics and antiferromagnetic spintronics, we present a method to realize ultrafast spin transport. The optical Barnett effect provokes quasiequilibrium Bose-Einstein condensates (BECs) of magnons associated with the fully spin-polarized state in insulating antiferromagnets (AFs). This optomagnonic Barnett effect enables us to exploit coherent magnons of high frequency over the conventional ones of (sub-) terahertz associated with the N\'eel magnetic order. We show that the macroscopic coherence of those optical magnon BECs induces a spin current across the junction interface of weakly coupled two insulating AFs, and this optomagnonic Josephson effect realizes ultrafast spin transport. The period of the optomagnonic Josephson oscillation is much shorter than the conventional one of the order of picoseconds. Thus we propose a way to realize ultrafast spin transport in AFs by means of the macroscopic coherence of optical magnon BECs.