Novel Phenomena Induced by Magnon-Magnon and Magnon-Spin Coupling

Abstract

Realization of novel topological phases in magnonic band structures represents a new opportunity for the development of spintronics and magnonics with low power consumption. While several approaches have been proposed for generating topological magnonic surface states, they usually require materials with either special crystal symmetries or artificially modulated structures that demand advanced nanofabrication techniques, both of which bring in inevitable difficulties in experiments.

In this thesis, I show that in antiparallelly aligned magnetic multilayers, the longrange, chiral dipolar interaction between propagating magnons generates bulk bands with non-zero Chern integers and magnonic surface states carrying chiral spin currents. The surface states are highly localized and can be easily toggled between non-trivial and trivial phases through an external magnetic field. The realization of chiral surface spin currents in this dipolarly coupled heterostructure represents a magnonic implementation of the coupled wire model that has been extensively explored in electronic systems. My work presents an easy-to-implement system for realizing topological magnonic surface states and low-dissipation spin current transport in a tunable manner. Besides the magnon-magnon coupling induced novel topological phases, I also explore the possibility of realizing a hybrid magnon-spin coupled system for state-of-the-art quantum computing.