Excitations of ordered insulating magnets gain renewed interest due to their potential topological properties and the natural realization of magnetic analogues of the celebrated topological models. Here, we study the topologically nontrivial multiplet excitations of the spin-$1/2$ kagome antiferromagnet with strong breathing anisotropy and Dzyaloshinskii-Moriya interaction. We show that in the chiral magnetic ground state the excitations can be characterized with a spin-$1/2$ doublet and a spin-$3/2$ quartet. Applying magnetic field, we can tune a band touching topological transition within the quartet band. At the transition point a spin-3/2 Dirac cone is formed by the touching of four bands. In the topologically nontrivial regime the spin-$3/2$ bands have large Chern numbers $-3,-1$, 1, 3. Furthermore, the chiral edge states appearing for open boundary condition naturally inherit the multipolar characters and we find novel quadrupolar edge modes.

• Received 3 October 2018

DOI:https://doi.org/10.1103/PhysRevB.99.014408