Magnon-skyrmion scattering in chiral magnets
Magnon-skyrmion scattering in chiral magnets
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DOI：
10.1103/physrevb.90.094423
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发表时间：
2014-09-30
影响因子：
3.7
通讯作者：
Garst, Markus
中科院分区：
文献类型：
--
作者：
Schuette, Christoph;Garst, Markus
手性磁体支持拓扑skyrmion纹理由于Dzyaloshinskiii-Moriya自旋轨道相互作用。在存在足够大的外加磁场时，这种skyrmions是场极化磁态的大振幅激发。我们解析地研究了这种skyrmion激发与其小振幅涨落之间的相互作用。例如，磁振子在一个干净的二维手征磁铁。的磁振子谱被发现包括两个磁振子skyrmion束缚态对应的呼吸模式，并为中间场，四极模式，这将引起子隙磁共振和电共振。由于skyrmion拓扑结构，磁振子从导致偏斜和彩虹散射的Aharonov-Bohm通量密度散射，其特征在于具有通常多个峰的不对称微分截面。作为斜散射的结果，有限密度的skyrmions将产生拓扑磁振子霍尔效应。利用能量-动量张量守恒定律，我们证明了磁振子也向Skyrmion传递动量。因此，磁振子电流导致磁振子压力，反映在斯太尔子运动的蒂勒方程中的动量转移力中。这种力是反应性的，并受Skyrmion散射截面的控制;它不仅导致有限的Skyrmion速度，而且还导致大的Skyrmion霍尔效应。我们的研究结果提供了，特别是，在清洁的绝缘手征磁体中的稀释Skyrmion气体的Skyrmion热电子学理论的基础。
Chiral magnets support topological skyrmion textures due to the Dzyaloshinskii-Moriya spin-orbit interaction. In the presence of a sufficiently large applied magnetic field, such skyrmions are large-amplitude excitations of the field-polarized magnetic state. We investigate analytically the interaction between such a skyrmion excitation and its small-amplitude fluctuations, i. e., the magnons in a clean two-dimensional chiral magnet. The magnon spectrum is found to include two magnon-skyrmion bound states corresponding to a breathing mode and, for intermediate fields, a quadrupolar mode, which will give rise to subgap magnetic and electric resonances. Due to the skyrmion topology, the magnons scatter from an Aharonov-Bohm flux density that leads to skew and rainbow scattering, characterized by an asymmetric differential cross section with, in general, multiple peaks. As a consequence of the skew scattering, a finite density of skyrmions will generate a topological magnon Hall effect. Using the conservation law for the energy-momentum tensor, we demonstrate that the magnons also transfer momentum to the skyrmion. As a consequence, a magnon current leads to magnon pressure reflected in a momentum-transfer force in the Thiele equation of motion for the skyrmion. This force is reactive and governed by the scattering cross sections of the skyrmion; it causes not only a finite skyrmion velocity but also a large skyrmion Hall effect. Our results provide, in particular, the basis for a theory of skyrmion caloritronics for a dilute skyrmion gas in clean insulating chiral magnets.