Xiuzhen Yu1,Naoya Kanazawa2,Xicao Zhang3,Konstantin Iakoubovskii1,Kiyomi Nakajima1,Masahito Mochizuki3,Yoshinori Tokura1
RIKEN1,The University of Tokyo2,Waseda University3
Xiuzhen Yu1,Naoya Kanazawa2,Xicao Zhang3,Konstantin Iakoubovskii1,Kiyomi Nakajima1,Masahito Mochizuki3,Yoshinori Tokura1
RIKEN1,The University of Tokyo2,Waseda University3
The spontaneous formation of vortex-antivortex pairs and their topological transitions have been extensively studied in various branches of physics, demonstrating their crucial role in phenomena such as superconductivity and quantum computing<sup>1</sup>. Unlike conventional magnets that typically exhibit collinear spin textures, helimagnets with non-centrosymmetric crystal structures offer additional degrees of freedom essential for manipulating noncollinear spin textures, such as a proper screw structure at zero field<sup>2</sup>. This unique characteristic makes helimagnets promising candidates for exploring and engineering topological states, such as a skyrmion lattice state, under specific conditions of temperature and external magnetic field<sup>3</sup>. However, achieving multiple topological magnetic states and their transitions within a single helimagnet presents a significant challenge due to the inherent topological protection associated with each state. <br/>In this talk, I will present real-space observations of a spontaneous vortex pair composed of a meron and an antimeron, possessing topological charges of <i>N</i> = ±1/2, respectively, in a helimagnet Fe<sub>0.5</sub>Co<sub>0.5</sub>Ge through advanced transmission electron microscopy. In addition, a meron pair, referred to as a bimeron (i.e., a vortex-antivortex pair), carrying a topological charge of <i>N</i> = −1, will also be presented. We successfully achieved the mutual transition between skyrmions and bimerons and the transformation of individual bimerons into a skyrmion lattice by carefully controlling the external magnetic field and electric current<sup>4</sup>.<br/>Overall, this research piece offers valuable insights into the manipulation of topological states, paving the way for potential future applications in fields such as spintronics and quantum technologies.<br/> *This work was supported in part by Grants-In-Aid for Scientific Research (A) (Grant No. 19H00660, 23H05431) from the Japan Society for the Promotion of Science (JSPS) and the Japan Science and Technology Agency (JST) CREST program (Grant No. JPMJCR1874, JPMJCR20T1), Japan.<br/> <br/>[1] L. Chibotaru, <i>et al.</i> <i>Nature</i> 408, 833 (2000).<br/>[2] Y. Tokura, and N. Kanazawa, <i>Chem. Rev.</i> 121, 2857 (2021).<br/>[3] N. Nagaosa, and Y. Tokura, <i>Nat. Nanotechnol.</i> 8, 899 (2013).<br/>[4] X. Z. Yu, et al. to be submitted.