Dynamic transition and Galilean relativity of current-driven skyrmions

• Published in: Nature (London) Vol. 633; no. 8030; pp. 554 - 559K
• Main Authors: Birch, Max T, Belopolski, Ilya, Fujishiro, Yukako, Kawamura, Minoru, Kikkawa, Akiko, Taguchi, Yasujiro, Hirschberger, Max, Nagaosa, Naoto, Tokura, Yoshinori
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 19.09.2024
• Subjects: Conduction; Conduction electrons; Electric fields; Electrodynamics; Electromagnetism; Electron drift velocity; Electron spin; Electrons; Hall effect; Hypothetical particles; Magnetic fields; Particle spin; Particle theory; Quantum transport; Real time; Relativity; Spin dynamics; Swirling; Topology; Transport phenomena; Velocity
• ISSN: 0028-0836; 1476-4687
• DOI: 10.138/s41586-024-07859-2

The coupling of conduction electrons and magnetic textures leads to quantum transport phenomena described by the language of emergent electromagnetic fields13. For magnetic skyrmions, spin-swirling particle-like objects, an emergent magnetic field is produced by their topological winding4 6, resulting in the conduction electrons exhibiting the topological Hall effect (THE)7. When the skyrmion lattice (Ski) acquires a drift velocity under conduction electron flow, an emergent electric field is also generated8,9. The resulting emergent electrodynamics dictate the magnitude of the THE by the relative motion of Ski and conduction electrons. Here we report the emergent electrodynamics induced by Ski motion in Gd2PdSi3, facilitated by its giant THE10,11. With increasing current excitation, we observe the dynamic transition of the Ski 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 Ski velocity-current profile, which shows the inertial-like motion of the Ski in the creep regime, appearing as the current hysteresis of the skyrmion velocity.