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arXiv 1802.04229cond-mat.mes-hallcond-mat.str-elcond-mat.supr-con
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作为长约瑟夫森结的易平面磁条

Easy-Plane Magnetic Strip as a Long Josephson Junction

Daniel Hill, Se Kwon Kim, Yaroslav Tserkovnyak

摘要:

对存在弱面内各向异性的易平面铁磁体(EPF)中的自旋力矩偏置磁动力学进行了理论研究。虽然这种各向异性破坏了U(1)对称性,从而淬灭了传统的自旋超流性,我们表明,该系统,而不是实现了一个密切的模拟长约瑟夫森结(LJJ)模型。后者的传统磁场和电流控制分别映射到施加在磁条两端的面外自旋力矩的对称和反对称组合上。这表明了在绝缘磁系统中实现超流体传输现象的另一种途径。研究了自旋力矩偏置相图,给出了EPF中静态多畴相的解析解。我们适应现有的LJJ的自洽性方法,开发一个近似的解决方案的EPF动态。LJJ-EPF映射允许我们设想高温下的超导电路功能。结果同样适用于反铁磁体与适当的有效自由能的Néel秩序,而不是磁化。

英文摘要:

Spin-torque-biased magnetic dynamics in an easy-plane ferromagnet (EPF) is theoretically studied in the presence of a weak in-plane anisotropy. While this anisotropy spoils U(1) symmetry thereby quenching the conventional spin superfluidity, we show that the system instead realizes a close analog of a long Josephson junction (LJJ) model. The traditional magnetic-field and electric-current controls of the latter map respectively onto the symmetric and antisymmetric combinations of the out-of-plane spin torques applied at the ends of the magnetic strip. This suggests an alternative route towards realizations of superfluid-like transport phenomena in insulating magnetic systems. We study spin-torque-biased phase diagram, providing an analytical solution for static multidomain phases in the EPF. We adapt an existing self-consistency method for the LJJ to develop an approximate solution for the EPF dynamics. The LJJ-EPF mapping allows us to envision superconducting circuit functionality at elevated temperatures. The results apply equally to antiferromagnets with suitable effective free energy in terms of the Néel order instead of magnetization.

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