Propagating spin excitations along skyrmion strings
Propagating spin excitations along skyrmion strings
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发表时间：
2019
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通讯作者：
S. Seki;M. Garst;J. Waizner;R. Takagi;Y. Okamura;K. Kondou;F. Kagawa;Y. Otani;Y. Tokura
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作者：
S. Seki;M. Garst;J. Waizner;R. Takagi;Y. Okamura;K. Kondou;F. Kagawa;Y. Otani;Y. Tokura
S. Seki、M. Garst、J. Waizner、R. Takagi、Y. Okamura、K. Kondou、F. Kakawa、Y. Otani 和 Y. Tokura 1 东京大学应用物理系，东京 113-8656，日本，2 RIKEN 突发物质科学中心 (CEMS)，和光 351-0198，日本，3 研究所理论物理学，德累斯顿工业大学，01062 德累斯顿，德国，4 科隆大学理论物理学研究所，Zülpicher Str。 77a, 50937 Köln, 德国, 5 固体物理研究所, 东京大学, 柏 277-8581, 日本 摘要 磁性斯格明子，一种以二维旋转自旋纹理为特征的拓扑孤子，最近作为稳定的类粒子物体而引起了人们的关注。在三维系统中，斯格明子可以在三维中延伸，形成坚固且灵活的弦结构，其独特的拓扑和对称性预计将承载重要的功能响应。在这里，我们通过实验证明了手性晶格磁体 Cu2OSeO3 的自旋激发沿斯格明子弦的相干传播。我们发现这种传播在方向上是不可逆的，并且不可逆的程度以及相关的群速度和衰减长度在很大程度上取决于激发模式的特征。我们的理论计算建立了相应的色散关系，很好地再现了实验观察到的特征。值得注意的是，这些自旋激发可以传播超过斯格明子直径 10 倍的距离，证明了斯格明子弦上激发传播的优异的长程性质。我们结合的实验和理论结果提供了对斯格明子弦激励的传播动力学的全面解释，并提出了沿着这种拓扑保护的弦单向信息传输的可能性。
S. Seki, M. Garst, J. Waizner, R. Takagi, Y. Okamura, K. Kondou, F. Kagawa, Y. Otani, and Y. Tokura 1 Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan, 2 RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan, 3 Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany, 4 Institut für Theoretische Physik, Universität zu Köln, Zülpicher Str. 77a, 50937 Köln, Germany, 5 Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan Abstract Magnetic skyrmions, topological solitons characterized by a two-dimensional swirling spin texture, have recently attracted attention as stable particle-like objects. In a three-dimensional system, a skyrmion can extend in the third dimension forming a robust and flexible string structure, whose unique topology and symmetry are anticipated to host nontrivial functional responses. Here, we experimentally demonstrate the coherent propagation of spin excitations along skyrmion strings for the chiral-lattice magnet Cu2OSeO3. We find that this propagation is directionally non-reciprocal, and the degree of non-reciprocity, as well as the associated group velocity and decay length, are strongly dependent on the character of the excitation modes. Our theoretical calculation establishes the corresponding dispersion relationship, which well reproduces the experimentally observed features. Notably, these spin excitations can propagate over a distance exceeding 10 times the skyrmion diameter, demonstrating the excellent long-range nature of the excitation propagation on the skyrmion strings. Our combined experimental and theoretical results offer a comprehensive account of the propagation dynamics of skyrmion-string excitations, and suggest the possibility of unidirectional information transfer along such topologicallyprotected strings.