  Valleytronics is a pioneering technological field relying on the valley
degree of freedom to achieve novel electronic functionalities. Topological
valley-polarized electrons confined to domain walls in bilayer graphene were
extensively studied in view of their potentials in valleytronics. Here, we
study the magnonic version of domain wall excitations in 2D honeycomb
ferromagnetic bilayers (FBL) with collinear order. In particular, we explore
the implications of Dzyaloshinskii-Moriya interaction (DMI) and electrostatic
doping (ED) on the existence and characteristics of 1D magnons confined to
layer stacking domain walls in FBL. The coexistence of DMI and ED is found to
enrich the topology in FBL, yet the corresponding domain wall magnons do not
carry a well-defined valley index. On the other hand, we show that layer
stacking domain walls in DMI-free FBL constitute 1D channels for ballistic
transport of topological valley-polarized magnons. Our theoretical results
raise hope towards magnon valleytronic devices based on atomically thin
topological magnetic materials.

Materials Science;Mesoscale and Nanoscale Physics;Quantum Physics