University of Connecticut

Events Calendar

PhD Dissertation Defense

Monday, July 25, 2022
1:00pm – 3:00pm

Storrs Campus

Graduate Student Donal Sheets, Department of Physics, University of Connecticut

Advances in Photon-Based Techniques for Correlated Materials and Applied Physics

This dissertation reports advances enabling experimental research in three research areas of current interest: synchrotron-based studies of electronic excitations in correlated materials, development of an ultra-sensitive laser-based system for generating and measuring strain waves, and applied research in response to the COVID-19 pandemic.

The first section describes the role of magnetism in identifying correlated electron phases and presents progress using synchrotron-based resonant inelastic X-ray scattering (RIXS) applied to mixed-valent Yb-based materials. In nonmagnetic semiconductor YbB6 we have studied the energy- and angle-dependent scattering, which clearly shows two distinct photon scattering processes. One of these features can be analyzed and interpreted with ab-initio calculations, while the second appears more universal. We will also present measurements of mixed valent YbAl3 and YbInCu4 which show low energy spectral weight ascribed to many-body resonances. Together, our results demonstrate the potential for RIXS to separately assess the localized and itinerant electronic states of correlated f-electron materials.

The second section details the experimental development of an interferometric femtosecond pump-probe apparatus for observing linear and nonlinear evolution of strain waves and elastic properties in films and single crystals. Using a variable repetition rate amplified Yb fiber laser and 16 ns optical delay, this apparatus enables high sensitivity measurements of surface displacement and change in reflectivity across the time axis. Progress towards the measurement of interacting strain waves and soliton generation near structural and magnetic transitions will be described.

Finally, the development of an apparatus to evaluate the filtrations efficiency and breathability of filters and respirators in response to the COVID-19 pandemic will be described. This apparatus can independently evaluate respirator and filter performance across a range of face velocities, pressure drops, and aerosolized particle sizes. This work has led to collaborations in broad public service, addressed high profile but erroneous claims on the efficacy of woven cloth respirators material, and contributed to developing a piezoelectric nanofiber membrane filter for application in biodegradable masks.

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Prof. J. Hancock

Physics Department (primary), College of Liberal Arts and Sciences, UConn Master Calendar

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