Spatially non-uniform ground state and quantized vortices in a two-component Bose-Einstein condensate of magnons
Spatially non-uniform ground state and quantized vortices in a two-component Bose-Einstein condensate of magnons
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DOI：
10.1038/srep00482
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发表时间：
2012-06-29
影响因子：
4.6
通讯作者：
Demokritov, S. O.
中科院分区：
文献类型：
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作者：
Nowik-Boltyk, P.;Dzyapko, O.;Demokritov, S. O.
磁性薄膜中的磁振子气体不同于所有其他已知的证明玻色-爱因斯坦凝聚（BEC）的系统，因为它拥有两个具有非零波矢量+/-k（BEC）的能量简并的最低能量量子态。因此，该系统中的 BEC 会产生自发形成的二组分玻色-爱因斯坦凝聚态，由两个空间非均匀波函数 α exp(+/-i(kBEC)z) 的线性组合描述，而其他物理系统中发现的凝聚态则以空间均匀波函数为特征。在这里，我们报告了一项具有亚微米空间分辨率的磁振子 BEC 的研究。我们通过实验证实了这两个波函数的存在，并表明它们的干涉导致凝聚态的基态不均匀，密度在空间中振荡。此外，我们观察到凝聚态中稳定的拓扑缺陷。通过将实验结果与基于 Ginzburg-Landau 方程的理论模型的预测进行比较，我们将这些缺陷识别为量子化涡流。
A gas of magnons in magnetic films differs from all other known systems demonstrating Bose-Einstein condensation (BEC), since it possesses two energetically degenerate lowest-energy quantum states with non-zero wave vectors +/-k(BEC). Therefore, BEC in this system results in a spontaneously formed two-component Bose-Einstein condensate described by a linear combination of two spatially non-uniform wave-functions alpha exp(+/-i(kBEC)z), while condensates found in other physical systems are characterized by spatially uniform wave-functions. Here we report a study of BEC of magnons with sub-micrometer spatial resolution. We experimentally confirm the existence of the two wave-functions and show that their interference results in a non-uniform ground state of the condensate with the density oscillating in space. Additionally, we observe stable topological defects in the condensate. By comparing the experimental results with predictions of a theoretical model based on the Ginzburg-Landau equation, we identify these defects as quantized vortices.