This article discusses two different coherent quantum phenomena of magnonic bosons: Bose–Einstein condensation (mBEC) and Superfluid State of Magnons (SSM). What is the difference between the two? Magnon BEC is a quantum phenomenon determined by local density of bosonic quasiparticles. The superfluid state of magnons is a long-range coherent quantum state characterized by the rigidity of the order parameter. This is similar to the states of mass superfluidity and superconductivity. In this state, the deflected magnetization can coherently precess even in a strongly inhomogeneous magnetic field. The magnons superflow restore the coherence of SSM after a perturbation. The critical Landau velocity of the coherent magnon flow is determined by an energy gap arising from the repulsion of magnons. This article describes in detail the mechanism of SSM formation.

中文翻译：

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磁超流与玻色凝聚

本文讨论了磁子玻色子的两种不同的相干量子现象：玻色-爱因斯坦凝聚 (mBEC) 和磁子的超流体态 (SSM)。两者有什么区别？Magnon BEC 是一种由玻色准粒子的局部密度决定的量子现象。磁振子的超流体态是一种长程相干量子态，其特点是有序参数的刚性。这类似于质量超流和超导的状态。在这种状态下，即使在强烈不均匀的磁场中，偏转的磁化强度也可以相干进动。磁振子超流在扰动后恢复 SSM 的相干性。相干磁振子流的临界朗道速度由磁振子排斥产生的能隙决定。