Theory of chiral gauge field in fully spin-polarized magnetic Weyl semimetal Co₃Sn₂S₂

Weyl semimetals exhibit pairs of gapless points (Weyl points) in momentum space. The Weyl points are distinguished by the chirality +1 or -1, which characterizes the topological nature of Weyl fermions. When the positions of the Weyl points are shifted by external perturbations, this effect serves as the chirality-dependent vector potential for the Weyl fermions, which is called the “chiral gauge field” in relativistic quantum field theory. The chiral gauge field picture is useful in understanding the magnetoelectric phenomena of Weyl semimetals under such perturbations.

In this talk, we present our theoretical analysis of the structure of the chiral gauge field in the ferromagnetic Weyl semimetal, Co₃Sn₂S₂. Co₃Sn₂S₂ is one of the typical materials for magnetic Weyl semimetals, exhibiting nearly full spin polarization due to the large spin splitting by spontaneous magnetization. Using an effective tight-binding model of Co₃Sn₂S₂, we first demonstrate the relation between the shift of Weyl points in momentum space and the direction of the magnetization. Based on this result, we show the spatial structure and magnitude of the chiral gauge field, when the domain wall is formed in Co₃Sn₂S₂. With this chiral gauge field picture, we propose that the domain wall dynamics induce a sizable electric current in Co₃Sn₂S₂, which arises as the Hall current driven by the chiral electromagnetic fields. This current may be useful for detecting the domain wall motion, in future spintronic devices based on Co₃Sn₂S₂.