EAPSI:Exploring Foundations for Energy-Efficient, Novel Computing Architectures

Daniels Matthew W, Pittsburgh PA

Investigators

Abstract

Magnetic materials are at the heart of many modern computing applications, and their continued study is crucial to the success of emerging information technologies. Magnetic properties are also of great scientific interest, playing a key role in many quantum mechanical systems. In a magnetic sample, the visible magnetic field is due to the cooperation among all the atoms in the sample which collude to add their microscopic fields together. In this case, all the atomic fields are parallel. In a typical non-magnet, the atomic fields are randomly aligned and sum to zero. But in some materials, the atoms can arrange their fields in coherent but nontrivial ways: such "magnetic textures" include spirals, vortices, and walls. When magnetic materials adopt these unusual atomic patternings, the system can be exploited to store and process information. This research aims to study the Berry phase physics that arises from interactions between magnons and spin textures in antiferromagnetic insulators. The research will be conducted in collaboration with Dr. Jiang Xiao, a noted expert on spin wave excitation in both ferromagnets and antiferromagnets, at Fudan University in China. This research will use a nonlinear sigma model formalism to provide a non-Abelian gauge theory for antiferromagnets. In particular, we apply the theory to antiferromagnetic skyrmion textures and search for topological phenomena such as non-trivial Berry phases and Hall effects. Though previous studies have demonstrated the absense of a skyrmion Hall effect in antiferromagnets, the research posits that there is evidence to suspect a chiral Hall effect when the driving magnon current is chirally polarized---a feature unique to antiferromagnetic spin waves. Numerical simulations, created in-house as part of this study, will be used to model these effects and detect topological effects by solving the Landau-Lifshitz-Gilbert equation on a lattice. This NSF EAPSI award supports the research of a U.S. graduate student and is funded in collaboration with the Chinese Ministry of Science and Technology.