Concurrence of topological electrons and magnons in the Kagome ferromagnet CoCu3(OH)6Cl2

Spin and charge are two interrelated properties of electrons. However, most of previous works on topological matter study the electronic and magnonic excitations separately. In this paper, by combining density functional theory calculations with the Schwinger boson method, we determine the topological electronic band structures and topological magnon spectrum simultaneously in the ferromagnetic ground state of the narrow-band-gap CoCu3(OH)6Cl2, which is an ABC stacking Kagome lattice material with fractional occupancy on Cu sites. This material provides an ideal platform to study the interplay of different types of topological excitations. Our work also proposes a useful method to deal with correlated topological magnetic systems with narrow band gaps.