Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
Phys Rev Lett. 2018 Aug 17;121(7):077203. doi: 10.1103/PhysRevLett.121.077203.
Evolution of an overpopulated gas of magnons to a Bose-Einstein condensate and excitation of a magnon supercurrent, propelled by a phase gradient in the condensate wave function, can be observed at room temperature by means of the Brillouin light scattering spectroscopy in an yttrium iron garnet material. We study these phenomena in a wide range of external magnetic fields in order to understand their properties when externally pumped magnons are transferred towards the condensed state via two distinct channels: a multistage Kolmogorov-Zakharov cascade of the weak-wave turbulence or a one-step kinetic instability process. Our main result is that opening the kinetic instability channel leads to the formation of a much denser magnon condensate and to a stronger magnon supercurrent compared to the cascade mechanism alone.
在钇铁石榴石材料中，通过布里渊光散射光谱学，我们可以在室温下观察到一个过稠密的磁振子气体演变为玻色-爱因斯坦凝聚态，以及在凝聚波函数的相位梯度推动下激发磁振子超流的现象。为了了解外部泵送磁振子通过两个不同的通道转移到凝聚态时的特性，我们在广泛的外部磁场范围内研究了这些现象：弱波湍流的多级柯尔莫哥洛夫-札卡哈罗夫级联或单步动力学不稳定性过程。我们的主要结果是，与级联机制相比，打开动力学不稳定性通道会导致形成更密集的磁振子凝聚态和更强的磁振子超流。
