Confinement of Bose-Einstein magnon condensates in adjustable complex magnetization landscapes

TL;DR

This paper demonstrates the control and confinement of magnon Bose-Einstein condensates in a magnetization landscape, enabling enhanced lifetime and dynamic manipulation of coherent magnon waves at room temperature.

Contribution

It introduces a method to spatially confine and control magnon BECs using optically patterned magnetization landscapes and magnon supercurrents.

Findings

Localized magnon accumulation due to supercurrents

Increased BEC lifetime from controlled confinement

Dynamic manipulation of magnon textures achieved

Abstract

Coherent wave states such as Bose-Einstein condensates (BECs), which spontaneously form in an overpopulated magnon gas even at room temperature, have considerable potential for wave-based computing and information processing at microwave frequencies. The ability to control the transport properties of magnon BECs plays an essential role for their practical use. Here, we demonstrate spatio-temporal control of the BEC density distribution through the excitation of magnon supercurrents in an inhomogeneously magnetized yttrium iron garnet film. The BEC is created by microwave parametric pumping and probed by Brillouin light scattering spectroscopy. The desired magnetization profile is prepared by heating the film with optical patterns projected onto its surface using a phase-based wavefront modulation technique. Specifically, we observe a pronounced spatially localized magnon accumulation caused by magnon supercurrents flowing toward each other originating in two heated regions. This accumulation effect increases the BEC lifetime due to the constant influx of condensed magnons into the confinement region. The shown approach to manipulate coherent waves provides an opportunity to extend the lifetime of freely evolving magnon BECs, create dynamic magnon textures, and study the interaction of magnon condensates formed in different regions of the sample.