Interactive Spin Dynamics in Magnon and Quantum Spin Systems

Abstract

Spintronics utilizes the intrinsic spin of electrons to design next-generation electronic devices, reducing power consumption and enabling innovative computing functions. Over the past decades, significant research interest has been directed toward two types of spin-based systems: collective excitations of spins, known as spin waves or magnons, in magnetic materials, and optically active spin defects as represented by nitrogen-vacancy (NV) centers in diamond, leading to the prosperity of magnonics, quantum sensing, and quantum information processing. As the understanding of dynamics in individual spin systems has deepened, recently there has been an increasing interest in the interactive dynamics within hybrid spin systems. This shift in focus reflects an increasing curiosity about how these complex interactions can be harnessed to further advance their microwave and quantum applications. However, several challenges persist, including the limited coherence length of magnons and the restricted frequency range of NV-based magnetometers, which will be tackled in this thesis. We first leverage the chirality of interlayer magnetic dipolar interactions to introduce an easily implementable system—antiparallel aligned magnetic multilayers—for realizing topological magnonic surface states and low-dissipation spin current transport in a tunable manner. We then expand the frequency window of NV-based magnetometers using nonlinear microwave-spin interactions, offering novel functionalities in quantum state control and sensing. We further exploit nonlinear spin dynamics by hybridizing NV centers with magnonic thin films, which not only amplifies the intensity of nonlinear resonance signals that are intrinsic to NV spins, but also enables novel frequency mixings through parametric pumping and nonlinear magnon scattering effects. We believe our study of interactive spin dynamics in hybrid systems involving magnons, quantum spin defects, and microwave photons help optimize these systems for a wide range of applications in both classical and quantum domains.