Quantization of the circulation of a magnon supercurrent was observed in a closed loop of yttrium-iron garnet film. Due to the low mass of magnons and their gaseous state at high concentrations, it was possible to obtain a magnon Bose-Einstein condensate at room temperature. [1].   According to the theory, the transition of magnons to a BEC state occurs when the precessing magnetization deviates by more than 2.5 degrees [2].    This phase transition has been experimentally observed precisely at this magnon concentration [3].  States with 2π and 4π circulation were observed. These states exhibit high stability. The circulation number is conserved under various changes in the phase difference of the radio-frequency pumping. It can be changed only by destroying and restoring the BEC with a new phase distribution. Thus, the magnon BEC possesses properties typical of the superfluid state! It should be noted that the kinematics of a magnon BEC is not described by the quasiclassical Landau-Lifshitz equations [1].  We also succeeded in creating a permanent magnon BEC using the method of auto-generation [4]. Thus, the magnon BEC represents a new platform for the development of quantum technologies at room temperature.

Fig.1. The phase shift of magnetization precession 4π along the YIG film ring

[1] G. A. Knyazev, A. N. Kuzmichev, P. E. Petrov, I. V. Savochkin, P. M. Vetoshko, V. I. Belotelov, and Yu. M. Bunkov, Optics Express 32, 13761-13768 (2024)
        [2] Yu. M. Bunkov, V. L. Safonov, J. Mag. Mag. Mat., 452,30–34 (2018)
        [3] P. E. Petrov, G. A. Knyazev, A. N. Kuzmichev, P. M. Vetoshko, V. I. Belotelov, and Yu. M. Bunkov, JETP Letters 119, 118 – 122 (2024).
        [4]. Yu. M. Bunkov, P. M. Vetoshko, G. A. Knyazev, A. N. Kuzmichev, D. A. Samodelkin, JETP Letters 123, 119-123, (2026).

Bunkov Yu. et al.,
JETP Letters 124, issue 7 (2026)