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In recent years, topological properties in electronic systems have been extensively studied in nonmagnetic materials and/or materials with simple magnetic structures (e.g. ferromagnets); on the other hand, there is also active research on the dynamics of real-space topological defects in various classical magnetic systems. Recently, we find that the band topology in momentum space and the magnetic topological defects in real space may interplay with each other in noncollinear antiferromagnetic Weyl semimetals Mn3Sn and CeAlGe. In Mn3Sn, we have theoretically studied the interplay between bulk Weyl electrons and the magnetic domains, domain walls, and Z6 magnetic vortex lines. We have argued that these materials possess a hierarchy of energy scales which allows a description of the spin structure and spin dynamics using a XY model with Z6 anisotropy. We have proposed a dynamical equation of motion for the XY order parameter, which implies the presence of magnetic domains and Z6 vortex lines, and the ability to control domains with currents. We have also introduced a minimal electronic model which allows for efficient calculations of the electronic structure and transport properties, unveiling Fermi arcs at domain walls which exhibit unique transport behavior.
In CeAlGe, the magnetoresistance was observed to have a singular angular dependence. We attribute such singular magnetoresistance to the formation of domains and domain walls in the presence of external magnetic fields along certain high-symmetry directions, and performed first principles calculations to study the coupling between the Weyl electrons and the local magnetic moments. |
