Mapping Domain Wall Topology in the Magnetic Weyl Semimetal CeAlSi

TL;DR

This study provides a detailed vector map of magnetization in CeAlSi, revealing complex domain wall topologies and magnetic structures that influence Weyl fermion interactions in this Weyl semimetal.

Contribution

It presents the first full vector mapping of local magnetization in CeAlSi, uncovering novel domain wall topologies and magnetic anisotropy phenomena linked to its noncollinear magnetic structure.

Findings

Identification of two types of domain walls with distinct topologies.

Discovery of emergent chirality in domain walls aligned along tetragonal axes.

Observation of splitting of easy axes into an octet below the magnetic transition.

Abstract

We report full vector mapping of local magnetization in CeAlSi, a Weyl semimetal in which both inversion and time-reversal symmetries are broken. The vector maps reveal unanticipated features both within domains and at their boundaries. Boundaries between domains form two kinds of walls with distinct topology and therefore different interactions with Weyl fermions. Domain walls aligned along the tetragonal axes, e.g. (100), exhibit emergent chirality forbidden by the bulk space group, while diagonal walls are non-chiral. Within the domains, we observe that the previously reported set of four easy axes aligned along the in-plane diagonals of the tetragonal structure actually split to form an octet with decreasing temperature below the magnetic transition. All the above phenomena are ultimately traced to the noncollinear magnetic structure of CeAlSi.