A research team from the High Magnetic Field Laboratory of the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, together with collaborators from Anhui University, ShanghaiTech University, and the University of New Hampshire, has demonstrated the first electrically controllable generation of hopfions—three-dimensional topological solitons—in a solid-state magnetic system.
The results were published online in Nature Materials.
Proposed in 1975, hopfions are three-dimensional topological structures characterized by a Hopf charge and capable of forming rings, links, and knots. Although they are predicted to exist in a wide range of physical systems—from magnetic materials and plasmas to the early universe—their complexity has kept hopfions largely confined to theory, with only limited experimental realization and control.
In this study, the researchers used a chiral magnet as a laboratory testbed. By applying spin-transfer torque together with thermal excitation, they successfully generated magnetic hopfions in the chiral magnet FeGe.
Importantly, the hopfions produced in this way are electrically controllable and remain stable even in the absence of an external magnetic field, representing a major advance beyond previous static observations. To directly visualize their three-dimensional structure, the team combined angle-dependent quantitative electron holography with micromagnetic simulations, enabling a detailed characterization of the rotational magnetic phase and an experimental confirmation of the hopfions' 3D topological configuration.
In addition, in-situ electrical measurements showed that the magnetic hopfions can be driven by electric currents. Unlike many other magnetic textures, they exhibit unconventional dynamics without Hall deflection, reflecting transport behavior that is fundamentally linked to their three-dimensional topology.
The work establishes a scalable, and controllable experimental platform for investigating hopfion dynamics and their universal physical properties, according to the team.
（a）Structure of a magnetic hopfion.（b）Experimental observation of the magnetic induction of the hopfion structure. (Image by LIU Yizhou)