A research team has achieved the first electrically controllable generation of hopfions—three-dimensional topological solitons—in a solid-state magnetic system. The groundbreaking findings were published in Nature Materials.
Hopfions, proposed in 1975, are three-dimensional topological structures characterized by a Hopf charge. While predicted to exist in various physical systems, from magnetic materials to plasmas, they have had limited experimental realization until this study.
In this pivotal research, scientists used a chiral magnet as a testbed. They successfully generated magnetic hopfions in the chiral magnet FeGe by applying spin-transfer torque alongside thermal excitation.
Representing a significant advance over previous static observations, the hopfions produced are electrically controllable and remain stable in the absence of an external magnetic field.
To visualize their intricate three-dimensional structure, the team combined angle-dependent quantitative electron holography with micromagnetic simulations. This enabled a detailed characterization of the rotational magnetic phase and an experimental confirmation of the hopfions' 3D topological configuration.
Further in-situ electrical measurements showed that these magnetic hopfions can be driven by electric currents. They exhibit unconventional dynamics without Hall deflection, reflecting transport behavior fundamentally linked to their three-dimensional topology.
This work establishes a scalable and controllable experimental platform for investigating hopfion dynamics and their universal physical properties.