Magnon confinement in a nanomagnonic waveguide by a magnetic Moir\'e superlattice

TL;DR

This paper demonstrates magnon confinement in a nanomagnonic waveguide using a magnetic moiré superlattice, revealing a flat magnon band that enables localized spin-wave trapping for potential magnonic devices.

Contribution

It introduces the concept of magnon confinement via a magnetic moiré superlattice, showing flat-band formation and magnon trapping in a nanostructured waveguide.

Findings

Discovery of a magnonic flat-band at the Brillouin zone center.

Magnon trapping within the AB stacking region due to mode anticrossing.

Spatial magnon confinement of 166 nm width.

Abstract

The study of moir\'e 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 moir\'e superlattice. Our numerical analysis reveals a magnonic flat-band at the centre of the Brillouin zone, created by a 3.5 degrees twist in the moir\'e superlattice. The flat-band, 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 flat-band results from the mode anticrossing of several different magnon bands, covering a wavevector range of nearly 40 rad/{\mu}m 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.