Topological antichiral edge states and one-way bulk states in patterned ferromagnetic thin films

The interfacial Dzyaloshinskii-Moriya interactions (iDMIs), occurring at the interfaces of the heavy metal and thin film, are anticipated to yield topologically nontrivial magnon modes, characterized by the Chern number. Based on the heterostructure consisting of a topologically trivial domain sandwiched between two nontrivial domains containing two distinct heavy metal dot arrays with opposite iDMI parameters, we present a theoretical proposal for the emergence of topological antichiral edge states and one-way bulk states, which possess remarkable immunity to backscattering and robustness against disorders. The features result in the generation of copropagating spin currents traveling at opposite edges, compensated by the counterpropagating spin currents confined within a large bulk area. Leveraging the greater tunability, flexibility, and extended transport areas associated with the one-way states, it becomes possible to design magnonic collimation devices. Our work offers us a way for observing intriguing physical phenomena and constructing low-dissipation magnonic devices.