Magnon confinement in a nanomagnonic waveguide by a magnetic Moiré superlattice

The study of moiré superlattices has revealed intriguing phenomena in electronic systems, including unconventional superconductivity and ferromagnetism observed in magic-angle bilayer graphene. This approach has recently been adapted to the field of magnonics. In this Letter, we investigate the confinement of spin waves in a nanomagnonic waveguide integrated on top of a magnetic moiré superlattice. Our numerical analysis reveals a magnonic flatband at the center of the Brillouin zone, created by a 3.5° twist in the moiré superlattice. The flatband, characterized by a high magnon density of states and a zero group velocity, allows for the confinement of magnons within the AB stacking region. The flatband results from the mode anticrossing of several different magnon bands, covering a wavevector range of nearly 40 rad/μm and a 166 nm wide spatial distribution of the magnon trapping in the waveguide. Our results pave the way for nanomagnonic devices and circuits based on spin-wave trapping in magnon waveguides.