Abstract

We report the experimental observation of the spin-wave moiré edge and cavity modes using Brillouin light scattering spectromicroscopy in a nanostructured magnetic moiré lattice consisting of two twisted triangle antidot lattices based on an yttrium iron garnet thin film. Spin-wave moiré edge modes are detected at an optimal twist angle and with a selective excitation frequency. At a given twist angle, the magnetic field acts as an additional degree of freedom for tuning the chiral behavior of the magnon edge modes. Micromagnetic simulations indicate that the edge modes emerge within the original magnonic band gap and at the intersection between a mini flatband and a propagation magnon branch. Our theoretical estimate for the Berry curvature of the magnon-magnon coupling suggests a nontrivial topology for the chiral edge modes and confirms the key role played by the dipolar interaction. Our findings shed light on the topological nature of the magnon edge mode for emergent moiré magnonics.

Alternate abstract:

Plain Language Summary

When two lattices are stacked and twisted at a small angle relative to one another, a new periodic pattern known as a moiré lattice appears. Moiré physics has recently led to extraordinary discoveries such as unconventional superconductivity and a new type of laser. But despite advances in electronic and photonic behaviors in moiré systems, there has been no experimental work on magnonics—a promising avenue for low-power computing and data processing that uses magnons, or spin waves, as information carriers. Here, we provide the first experimental evidence of magnons in a moiré system.

In our study, we fabricate a nanostructured magnetic moiré lattice on a yttrium iron garnet thin film. In experiments, we observe emergent spin-wave modes propagating at the edge of a moiré unit cell. The magnon edge mode becomes best defined at an optimal twist angle between the two sublattices of 6 degrees and is controllable with an applied magnetic field. We observe an additional mode at the center of a moiré unit cell with a different resonance frequency from the edge mode. The asymmetric propagation observed for the edge mode indicates its chirality associated with the moiré magnon band structure as studied by micromagnetic simulations. Our theoretical estimates of the magnon-magnon coupling between two twisted lattices via dipolar interactions reveal the topological nature of the chiral edge modes.

Our findings provide a key initiative in an emergent research field of moiré magnonics, in which the use of topologically protected magnon edge modes will significantly enhance the capabilities of magnonic devices for information processing.

Details

Title
Observation of Spin-Wave Moiré Edge and Cavity Modes in Twisted Magnetic Lattices
Author
Wang, Hanchen  VIAFID ORCID Logo  ; Madami, Marco; Chen, Jilei; Jia, Hao; Zhang, Yu; Yuan, Rundong  VIAFID ORCID Logo  ; Wang, Yizhan; He, Wenqing; Sheng, Lutong; Zhang, Yuelin; Wang, Jinlong; Liu, Song; Shen, Ka  VIAFID ORCID Logo  ; Yu, Guoqiang; Han, Xiufeng; Yu, Dapeng; Jean-Philippe Ansermet; Gubbiotti, Gianluca  VIAFID ORCID Logo  ; Yu, Haiming  VIAFID ORCID Logo 
Publication year
2023
Publication date
Apr-Jun 2023
Publisher
American Physical Society
e-ISSN
21603308
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2807661540
Copyright
© 2023. This work is licensed under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.