Ginzburg-Landau theory for skyrmions in inversion-symmetric magnets with competing interactions
Ginzburg-Landau theory for skyrmions in inversion-symmetric magnets with competing interactions
复制标题
DOI：
10.1103/physrevb.93.064430
复制
发表时间：
2016-02-25
影响因子：
3.7
通讯作者：
Hayami, Satoru
中科院分区：
文献类型：
--
作者：
Lin, Shi-Zeng;Hayami, Satoru
近年来，磁性天幕因其在自旋电子学中的巨大应用潜力而引起了人们的广泛关注。一般来说，skyrmions比原子晶格常数大，这使得连续体极限中的金兹堡-朗道型描述成为可能。这样的描述成功地捕捉到了B20化合物中无反演对称性的天团的主要实验观测结果。Skyrmions也可以存在于具有竞争相互作用的反转对称磁体中。在这里，我们导出了在长波长限制下有效的磁体中skyrmions的一般金兹堡-朗道理论。基于推导出的金兹堡-朗道理论，我们研究了天球不同寻常的静态和动态特性。我们证明了一个简单的轴自旋各向异性足以稳定一个斯基子晶格。有趣的是，逆对称磁体中的skyrmions除了通常的skyrmions的平移运动（轨道运动）之外，还具有与螺旋度旋转相关的新的内部自由度，即skyrmions作为粒子的“自旋”。单个skyrmions的轨道自由度和自旋自由度可以相互耦合，并产生由Dzyaloshinskii-Moriya相互作用稳定的skyrmions所没有的不寻常行为。推导出的金兹堡-朗道理论提供了一个方便和通用的框架来讨论skyrmions物理，并将有助于在反转对称磁体中寻找skyrmions。
Magnetic skyrmions have attracted considerable attention recently for their huge potential in spintronic applications. Generally skyrmions are big compared to the atomic lattice constant, which allows for the Ginzburg-Landau type description in the continuum limit. Such a description successfully captures the main experimental observations on skyrmions in B20 compound without inversion symmetry. Skyrmions can also exist in inversion-symmetric magnets with competing interactions. Here, we derive a general Ginzburg-Landau theory for skyrmions in these magnets valid in the long-wavelength limit. We study the unusual static and dynamical properties of skyrmions based on the derived Ginzburg-Landau theory. We show that an easy axis spin anisotropy is sufficient to stabilize a skyrmion lattice. Interestingly, the skyrmion in inversion-symmetric magnets has a new internal degree of freedom associated with the rotation of helicity, i.e., the "spin" of the skyrmion as a particle, in addition to the usual translational motion of skyrmions (orbital motion). The orbital and spin degree of freedoms of an individual skyrmion can couple to each other, and give rise to unusual behavior that is absent for the skyrmions stabilized by the Dzyaloshinskii-Moriya interaction. The derived Ginzburg-Landau theory provides a convenient and general framework to discuss skyrmion physics and will facilitate the search for skyrmions in inversion-symmetric magnets.