RIKEN Center for Emergent Matter Science (CEMS), Wakō, Japan.
Department of Applied Physics, University of Tokyo, Tokyo, Japan.
Nature. 2024 Sep;633(8030):554-559. doi: 10.1038/s41586-024-07859-2. Epub 2024 Sep 18.
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 GdPdSi, 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.
传导电子与磁织构的耦合导致了量子输运现象，这些现象可以用新兴电磁场的语言来描述。对于磁斯格明子（skyrmion），即具有自旋旋转的类粒子物体，其拓扑涡旋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 skyrmion 晶格（SkL）在传导电子流的作用下获得漂移速度时，也会产生一个新兴电场。由此产生的新兴电动力学通过 SkL 和传导电子的相对运动来决定 THE 的大小。在这里，我们报告了在 GdPdSi 中 SkL 运动引起的新兴电动力学，这得益于其巨大的 THE。随着电流激励的增加，我们观察到 SkL 运动从钉扎到蠕动再到流动的动态转变，在流动状态下，THE 完全被抑制。我们认为，即使在像本化合物这样的复杂多带系统中，也可能普遍恢复完全抵消 THE 所需的伽利略相对性。此外，观察到的 THE 电压足够大，可以实时测量 SkL 速度-电流曲线，这表明 SkL 在蠕动状态下具有惯性运动，表现为 skyrmion 速度的电流滞后。
