Slowdown of photoexcited spin dynamics in the non-collinear spin-ordered phases in skyrmion host GaV4S8

Formation of magnetic order alters the character of spin excitations, which then affects transport properties. We investigate the photoexcited ultrafast spin dynamics in different magnetic phases in Neel-type skyrmion host GaV4S8 with time-resolved magneto-optical Kerr effect experiments. The coherent spin precession, whose amplitude is enhanced in the skyrmion-lattice phase, shows a signature of phase coexistence across the magnetic phase transitions. The incoherent spin relaxation dynamics slows down by a factor of two in the skyrmion-lattice/cycloid phases, indicating significant decrease in thermal conductivity triggered by a small change of magnetic field. The slow heat diffusion in the skyrmion-lattice/cycloid phases is attributed to the stronger magnon scattering off the domain walls formed in abundance in the skyrmion-lattice/cycloid phase. These results highlight the impact of spatial spin structure on the ultrafast heat transport in spin systems, providing a useful insight for the step toward ultrafast photocontrol of the magnets with novel spin orders. Skyrmions are a topological magnetic texture that have garnered considerable interest for various technological applications. Here, Sekiguchi et al. investigate the ultrafast optical response of GaV4S6, and find a significant reduction in the thermal conductivity in the skyrmion phase.

Automated summary

The formation of magnetic order affects spin excitations and transport properties. In this study, the ultrafast spin dynamics in different magnetic phases of GaV4S8 were investigated using time-resolved magneto-optical Kerr effect experiments. The results show that the amplitude of coherent spin precession is enhanced in the skyrmion-lattice phase, indicating phase coexistence across magnetic phase transitions. Furthermore, the incoherent spin relaxation dynamics slows down in the skyrmion-lattice/cycloid phases, leading to a significant decrease in thermal conductivity. This is attributed to the increased magnon scattering off the domain walls formed in abundance in the skyrmion-lattice/cycloid phase. These findings provide insight into the impact of spatial spin structure on ultrafast heat transport in spin systems.