  Realization of novel topological phases in magnonic band structures
represents a new opportunity for the development of spintronics and magnonics
with low power consumption. In this work, we show that in antiparallelly
aligned magnetic multilayers, the long-range, chiral dipolar interaction
generates bulk bands with non-zero Chern integers and magnonic surface states
carrying chiral spin currents. The surface states are strictly localized and
can be easily toggled between non-trivial and trivial phases through an
external magnetic field. The realization of chiral surface spin currents in
this dipolarly coupled heterostructure represents a magnonic implementation of
the coupled wire model that has been extensively explored in electronic
systems. Our work presents an easy-to-implement system for realizing
topological magnonic surface states and low-dissipation spin current transport
in a tunable manner.
