Supercurrent in a room temperature Bose-Einstein magnon condensate

TL;DR

This study provides experimental evidence of supercurrent phenomena in a room temperature magnon Bose-Einstein condensate, demonstrating how thermal gradients induce phase gradients leading to supercurrent flow.

Contribution

It is the first demonstration of supercurrent in a room temperature magnon Bose-Einstein condensate, linking thermal gradients to supercurrent formation.

Findings

Thermal gradients induce a phase gradient in the magnon condensate.

Local heating affects the condensate's decay dynamics.

Supercurrent is observed due to temperature-induced phase gradients.

Abstract

We report evidence for the existence of a supercurrent of magnons in a magnon Bose-Einstein condensate prepared in a room temperature yttrium-iron-garnet magnetic film and subject to a thermal gradient. The magnon condensate is formed in a parametrically populated magnon gas, and its temporal evolution is studied by time-, frequency- and wavector-resolved Brillouin light scattering spectroscopy. It has been found that local heating in the focal point of a probing laser beam enhances the temporal decrease in the density of the freely evolving magnon condensate after the termination of the pumping pulse, but it does not alter the relaxation dynamics of the gaseous magnon phase. This phenomenon is understood as the appearance of a magnon supercurrent within the condensate due to a temperature- and, consequently, magnetisation-gradient induced phase gradient in the condensate wave function.