[PAST EVENT] Patrick McArdle: Physics Dissertation Defense  

April 14, 2022
1pm - 4pm

Patrick McArdle, Final Oral Examination for the Ph.D. Degree, Title: "Broadband Infrared Microspectroscopy and Nanospectroscopy of Local Material Properties: Experiment and Modeling"
Meeting ID: 97740510350 Passcode: available upon request. Please email Ellie at evwilk@wm.edu.

The study of infrared phenomena at micrometer and nanometer length scales can elucidate fundamental physics in highly correlated and complex systems. However, accessing these small lengths scales requires high resolution instrumentation and advanced analysis methods to extract meaningful information. Nearly diffraction limited broadband far-field infrared microscopy was implemented and used for secondary structural characterization in single strands of spider silk and for identification of an exotic metallic state through a high temperature phase transition in microcrystal Li2RuO3 (LRO). The sub diffraction limited experimental technique, scattering type near-field infrared microscopy (S-SNIM) was then used to identify nanoscale domains in LRO crystals. S-SNIM can circumvent the diffraction limit and access the nanoscale through the interaction between an illuminated atomic force microscope tip and sample of interest. Backscattered fields provide information about the local interaction between the tip apex (~20 nm) and sample. A numerical model to describe the S-SNIM interaction between tip and sample was developed to describe a wide range of materials including polaritonic resonances, multilayers, nanostructures, and anisotropic materials. This provides a blueprint for a universal modeling approach in S-SNIM. Finally, the numerical approach is applied for assessing the origin of the observed near-field LRO domain contrast.

Bio: Patrick was born in New Jersey and raised in Florida. In 2013 he graduated from University of Florida with a BS in Physics. He joined William & Mary in the fall of 2015 to pursue a Ph.D. He started working with Mumtaz Qazilbash and the photon spectroscopy group in 2017, with research focus on infrared microscopy of heterogenous and correlated materials.