Twist-Tuned Magnonic Nanocavity Mode in a Trilayer Moiré Superlattice.

The concept of moiré superlattices has recently been introduced into the field of magnonics, providing a route to control spin-wave propagation and confinement in nanoscale magnonic devices. In this work, we report a numerical investigation on the nanocavity mode in a trilayer magnetic moiré superlattice structure consisting of antidot lattices. By controlling 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 approximate optimal twist angle of 3°, excitation at the flat band frequency yields nanocavity mode with a line width of 175 nm. In contrast to its bilayer counterpart, the trilayer magnonic moiré superlattice introduces two interlayer coupling interfaces and supports three collective magnetization precession modes. The observed flat band is associated with antiphase nanocavity modes in the bottom and top 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 moiré structure offers a twist-dependent tunability for the design of future moiré magnonic devices.