In collaboration with German and Japanese researchers, BME Institute of Physics researchers investigated topological magnets using magneto-optical spectroscopy. They determined the magnetic field dependence of the low-energy excitations of one of the best-known magnetic Weyl semimetals, Co₃Sn₂S₂. By comparing their experimental results with ab initio calculations, they demonstrated that by varying the direction of magnetization, the characteristic degeneracies of the electronic band structure can be controlled, for example, the number of Weyl points can be tuned, and the appearance of line-like degeneracies (nodal loops) can be triggered.

F. Schilberth, M.-C. Jiang, F. Le Mardelé, L. B. Papp, I. Mohelsky, M. A. Kassem, Y. Tabata, T. Waki, H. Nakamura, G.-Y. Guo, M. Orlita, R. Arita, I. Kézsmárki & S. Bordács
Generation of a nodal line and Weyl points by magnetization reorientation in Co₃Sn₂S₂
npj Quantum Materials 10, 67 (2025)
https://www.nature.com/articles/s41535-025-00785-0