Probing Magnon Dynamics and Magnetic Order at the Nanoscale using nitrogen-vacancy (NV) magnetometry

Dissertation Committee Chair: Prof. Ron Walsworth
 

Committee:
Prof. Amir Yacoby
Prof. Christopher Jarzynski
Prof. Victor Yakovenko
Prof. John Cumings
 

Abstract:  We develop and apply nitrogen-vacancy (NV) center quantum sensing techniques in diamond to investigate magnetic excitations and ordering in condensed matter systems. We utilize micrometer-scale, (111)-oriented diamond chips with shallow NV ensembles as a platform for high-resolution quantum microscopy, demonstrating diffraction-limited imaging and deterministic transfer onto diverse materials. We introduce a broadband spectrum analyzer based on qubit dressed states that extends noise magnetometry using a novel protocol via the AC Stark shift, and apply it to measure the magnon spectrum of yttrium iron garnet (YIG). Using spatially-resolved NV magnetometry, we then image nonlinear magnon dynamics in YIG, extracting four-magnon interaction strengths and discovering cascaded parametric instabilities that reveal the discrete scattering pathways through which the magnon gas redistributes energy before thermalization. Finally, we image magnetization reversal in a pinwheel artificial spin ice, resolving superferromagnetic domain switching.