Experimental observation of Josephson oscillations in a room-temperature Bose-Einstein magnon condensate

TL;DR

This paper reports the first observation of the ac Josephson effect in a room-temperature magnon Bose-Einstein condensate, demonstrating macroscopic quantum phenomena at ambient conditions with potential applications in magnon spintronics.

Contribution

It presents the experimental discovery of Josephson oscillations in a room-temperature magnon BEC, extending quantum effects to ambient conditions.

Findings

Observation of Josephson oscillations in magnon BEC at room temperature

Demonstration of phase coherence between magnon condensates

Potential for quantum phenomena applications in spintronics

Abstract

The alternating current (ac) Josephson effect in a time-independent spatially-inhomogeneous setting is manifested by the occurrence of Josephson oscillations - periodic macroscopic phase-induced collective motions of the quantum condensate. So far, this phenomenon was observed at cryogenic temperatures in superconductors, in superfluid helium, and in Bose-Einstein condensates (BECs) of trapped atoms. Here, we report on the discovery of the ac Josephson effect in a magnon BEC carried by a room-temperature ferrimagnetic film. The BEC is formed in a parametrically populated magnon gas in the spatial vicinity of a magnetic trench created by a dc electric current. The appearance of the Josephson effect is manifested by oscillations of the magnon BEC density in the trench, caused by a coherent phase shift between this BEC and the BEC in the nearby regions. Our findings advance the physics of room-temperature macroscopic quantum phenomena and will allow for their application for data processing in magnon spintronics devices.