在YIG薄膜中自旋超流性是可能的吗？
Is spin superfluidity possible in YIG films?
摘要：
最近有人提出，在强外泵浦下，在钇铁石榴石（YIG）磁性薄膜中观察到的磁振子凝聚体中可能存在稳定的自旋超流（自旋超流）。我们在这里分析一下这个建议。从YIG的平衡态序参量的拓扑结构来看，我们不能期望有能垒使自旋超电流亚稳。然而，一些动力学起源的小障碍是可能的。临界相位梯度（类似于超流体中的朗道临界速度）与相干自旋波的强度（凝聚磁振子的数量）成正比。结论是，虽然在YIG薄膜自旋超流性是可能的，在原则上，它的观察是不合理的公开声明。分析表明，广泛接受的自旋波光谱在YIG薄膜的静磁和交换相互作用需要修改。这导致了对非线性修正的修正，非线性修正决定了有和没有自旋超流的磁振子凝聚体的稳定性。
英文摘要：
Recently it was suggested that stationary spin supercurrents (spin superfluidity) are possible in the magnon condensate observed in yttrium-iron-garnet (YIG) magnetic films under strong external pumping. Here we analyze this suggestion. From topology of the equilibrium order parameter in YIG one must not expect energetic barriers making spin supercurrents metastable. However some small barriers of dynamical origin are possible nevertheless. The critical phase gradient (analog of the Landau critical velocity in superfluids) is proportional to intensity of the coherent spin wave (number of condensed magnons). The conclusion is that although spin superfluidity in YIG films is possible in principle, the published claim of its observation is not justified. The analysis revealed that the widely accepted spin-wave spectrum in YIG films with magnetostatic and exchange interaction required revision. This led to revision of non-linear corrections, which determine stability of the magnon condensate with and without spin supercurrents.
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