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Events on Thursday, February 6th, 2020

R. G. Herb Condensed Matter Seminar
Studying superconductors using NV-centers in diamond optical magnetometry
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Ruslan Prozorov, Iowa State/Ames Lab
Abstract: The variation of magnetic fields across the superconducting samples is quite small in the fragile genuine Meissner state, which is easily disturbed by Abrikosov vortex pining and field inhomogeneities due to large demagnetization effects. We developed minimally invasive optical magneto-sensing based on the ensembles of NV centers in diamond crystal to study Meissner state structure and to determine the lower critical field. I will show how different the structure of the Meissner state is in different superconducting materials. I will also discuss the application of the NV sensing to identify quantum phase transition in charge-doped iron-based superconductors.
Host: Alex Levchenko
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Cosmology Journal Club
Time: 12:00 pm - 1:00 pm
Place: 5242 Chamberlin Hall
Abstract: We discuss papers from related to cosmology each week. All are welcome and feel free to bring your lunch. If there is a paper you would like to present, or have questions or comments, please email Ross Cawthon ( and Santanu Das (
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Astronomy Colloquium
X-raying the Intersellar Medium
Time: 3:30 pm - 5:00 pm
Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM, Talk begins 3:45 PM
Speaker: Dr. Eddie Schalfly, Lawrence Berkeley National Laboratory
Abstract: The interstellar medium (ISM) is the fuel of star formation, and its scattering and absorption of light transforms the Galactic radiation field. Despite its importance, most observations of the Milky Way's ISM are limited to two dimensions; its angular distribution is precisely measured, but its distribution in distance is much more uncertain. Large surveys of stars can be used to resolve this uncertainty. Because light from stars is absorbed and scattered by intervening material before observation on earth, the Galaxy's stars can be used as a dense network of lighthouses, effectively x-raying the ISM to reveal its 3D structure and properties. In this talk, I'll describe our ongoing program to use large surveys to map the ISM in 3D. We have mapped the density of dust in the ISM over the nearest 5 kpc at unprecedented resolution, highlighting complex networks of diffuse voids and dense star-forming regions. We have also been able to measure the size distribution of dust grains throughout the Milky Way, revealing kiloparsec-scale structures that may track variations in the Galactic star-formation rate and gas density. Numerous other projects are possible, ranging from studies of the 3D kinematics of the ISM to the Galactic magnetic field. New surveys and instruments like Gaia, SDSS-V, LSST, and JWST promise a bright future for 3D studies of the ISM, offering incredibly accurate distance measurements, order-of-magnitude larger samples of stars, and unrivalled sensitivitity.
Host: Bob Benjamin, UWM
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