Twist-Tuned Magnonic Nanocavity Mode in a Trilayer Moir\'e Superlattice
The concept of moir\'e superlattices has recently been introduced into the field of magnonics, enabling unprecedented control over spin-wave propagation and confinement in nanoscale magnonic devices. In this work, we report a numerical investigation on the nanocavity in a trilayer magnetic moir\'e superlattice structure consisting of antidot lattices. By tuning the middle layer twist angle, high tunability of the magnonic band structure can be achieved with characteristic flat bands and the corresponding nanocavity mode formation in outer layers. At an optimal twist angle of 3 deg, excitation at the flat band frequency yields nanocavity mode with linewidth of 175 nm. In contrast to its bilayer counterpart, the trilayer magnonic moir\'e superlattice exhibits antiphase nanocavity modes in the outer layers while showing no nanocavity formation in the middle layer. Our study indicates that the switching and distribution of the nanocavity modes can be governed by tuning the middle layer twist angle with a strong magnon intensity confinement. The trilayer magnonic moir\'e structure holds a distinct advantage in tunability, which opens up new avenues for the design of future moir\'e magnonic devices.