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Events on Friday, December 8th, 2023

Graduate Program Event
Preliminary Exam
Detection and Characterization of Core Magnetic Fluctuations on DIII-D using Faraday-Effect Polarimetry
Time: 1:30 pm - 3:30 pm
Place: 2301 Sterling
Speaker: Rachel Myers, Department of Physics Graduate Student
Abstract: Internal, resistive MHD instabilities called tearing modes (TMs) significantly contribute to disruptions and confinement degradation in tokamaks. Measuring nonlinear TM coupling with high m/n near the magnetic axis can aid in understanding neoclassical TM seeding, growth, and decay. For this tracking, we use the Radial Interferometer-Polarimeter (RIP), which is sensitive to core-resonant magnetic fluctuations on DIII-D and has detected TMs well before they appear on edge magnetic sensing coils [Pandya, DPP invited talk 2021]. Here we employ RIP to analyze the impact on pre-existing TMs of multiple, emerging MHD modes that are never detected by the coils. In one example, RIP detects a higher-frequency mode coupled to both an n=2 mode and a lower-frequency mode that later diminishes. All three modes are resonant near the magnetic axis, and their interaction is only visible using RIP. In this talk we will also discuss tearing mode structure and its potential effects on RIP-measured tearing mode amplitudes.

Zoom link:
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Graduate Program Event
Q&A with ISS representative
Time: 2:15 pm - 3:00 pm
Place: 2241 Chamberlin
Abstract: Sara Sheibani from ISS will be joining us. She will have a short presentation about ISS and then we’ll have plenty of time for questions. I encourage you to pose questions in advance, but feel free to just bring them along, too. Questions ahead can be added here: Hope to see you there! p.s. Come to ask questions. . .or come for the bagels and coffee! Either way, come join us!
Host: Sharon Kahn and Arifa
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Physics Department Colloquium
Origins of nematicity and field-induced superconductivity in iron-based materials
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Shua Sanchez, Postdoctoral Fellow, MIT
Abstract: Materials with strongly correlated electrons can give rise to interesting and useful phenomena, such as nematicity, magnetism, and unconventional superconductivity. In these systems, the charge, spin, and lattice degrees of freedom become intertwined, such that the origin of these phenomena becomes obscured. In this talk, I will discuss a new experimental platform which combines tunable applied strain, transport measurements, and several x-ray techniques to probe the origin and mechanisms of strongly correlated phases. I will review three recent studies in iron-based superconductors, which examine (1) the transport-structural correspondence in the nematic phase of doped BaFe2As2, (2) the orbital driver of nematicity in FeSe, and (3) the mechanism of field-induced superconductivity in ferromagnetic doped EuFe2As2. These diverse investigations demonstrate the power and promise of multimodal characterization for solving other puzzles in strongly correlated materials.

Sanchez, et al. Nature Materials (2021) DOI: 10.1038/s41563-021-01082-4
Occhialini and Sanchez, et al., Nature Materials (2023) DOI: 10.1038/s41563-023-01585-2
Sanchez, et al. Science Advances (2023) DOI: 10.1126/sciadv.adj520

Host: Victor brar
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