近日，日本RIKEN新兴物质科学中心(CEMS)的Yoshinori Tokura&Max T. Birch及其研究团队取得一项新进展。经过不懈努力，他们揭示电流驱动斯格明子的动态跃迁和伽利略相对性。相关研究成果已于2024年9月18日在国际权威学术期刊《自然》上发表。

本文报道了在Gd₂PdSi₃中，由其显著的拓扑霍尔效应（THE）所促进的斯格明子晶格（SkL）运动引发的新兴电动力学现象。随着电流激励的增加，研究人员观察到斯格明子晶格运动从钉扎状态到蠕变状态，并最终进入流动状态的动态转变，在此流动状态下，拓扑霍尔效应被完全抑制。

研究人员认为，即使在如本化合物这类复杂的多带系统中，实现拓扑霍尔效应完全抵消所需的伽利略相对性也可能在流动状态下普遍恢复。此外，所观测到的拓扑霍尔效应电压足够大，使得能够实时测量斯格明子晶格速度与电流的关系，该关系揭示了蠕变状态下斯格明子晶格类似惯性的运动，表现为斯格明子速度的电流滞后现象。

据悉，传导电子与磁结构的耦合产生了可由新兴电磁场理论描述的量子输运现象。对于磁斯格明子（一种自旋涡旋的粒子状物体）而言，其拓扑缠绕会产生一个新兴磁场，导致传导电子表现出拓扑霍尔效应（THE）。当斯格明子晶格（SkL）在传导电子流下获得漂移速度时，还会产生一个新兴电场。由此产生的新兴电动力学通过斯格明子晶格与传导电子的相对运动来决定拓扑霍尔效应的大小。

附：英文原文

Title: Dynamic transition and Galilean relativity of current-driven skyrmions

Author: Birch, Max T., Belopolski, Ilya, Fujishiro, Yukako, Kawamura, Minoru, Kikkawa, Akiko, Taguchi, Yasujiro, Hirschberger, Max, Nagaosa, Naoto, Tokura, Yoshinori

Issue&Volume: 2024-09-18

Abstract: The coupling of conduction electrons and magnetic textures leads to quantum transport phenomena described by the language of emergent electromagnetic fields. For magnetic skyrmions, spin-swirling particle-like objects, an emergent magnetic field is produced by their topological winding, resulting in the conduction electrons exhibiting the topological Hall effect (THE). When the skyrmion lattice (SkL) acquires a drift velocity under conduction electron flow, an emergent electric field is also generated. The resulting emergent electrodynamics dictate the magnitude of the THE by the relative motion of SkL and conduction electrons. Here we report the emergent electrodynamics induced by SkL motion in Gd₂PdSi₃, facilitated by its giant THE. With increasing current excitation, we observe the dynamic transition of the SkL motion from the pinned to creep regime and finally to the flow regime, in which the THE is totally suppressed. We argue that the Galilean relativity required for the total cancellation of the THE may be generically recovered in the flow regime, even in complex multiband systems such as the present compound. Moreover, the observed THE voltages are large enough to enable real-time measurement of the SkL velocity–current profile, which shows the inertial-like motion of the SkL in the creep regime, appearing as the current hysteresis of the skyrmion velocity.

DOI: 10.1038/s41586-024-07859-2

Source: https://www.nature.com/articles/s41586-024-07859-2