Physics and Astronomy Calendar

Week of Monday, November 18th 2019


Monday, November 18th 2019
12:15 pm:
Speaker: Larry Rudnick, UMN
Subject: Radiation from black holes, fundamental constants, multi-messengers at the solar mass scale: tidbits from the Astro2020 White Papers

White papers over the last year were submitted by the community to
provide their hopes and dreams for the next decade. I will briefly
review an eclectic selection of them, including electromagnetic
signatures from newly forming massive black holes, spectral probes of
the cosmic evolution of fundamental constants, predictions for
multi-messenger signatures of merging solar mass black holes, and other
interesting tidbits yet to be identified.


Tuesday, November 19th 2019
1:25 pm:
Space Physics Seminar in Tate 201-20
Speaker: Cynthia Cattell and Lindsay Glesener
Subject: Periodicities in Type III radio bursts observed by Parker Solar Probe and in coronal active regions

Periodicities have frequently been reported across many wavelengths in the solar corona. We focus on coordinated observations of Type III radio busts from the Fields instrument on Parker Solar Probe, of EUV emissions in the 211A and 171A bands by the SDO/AIA, and of solar flare x-rays by Nuclear Spectroscopic Telescope Array (NuSTAR) on April 12, 2019. Periodicities of ~ 5 minutes in the EUV in several areas of an active region are well correlated with the repetition rate of the Type III radio bursts. Detrended 211A light curves show periodic sawtooth profiles in one area, with rapid drops occurring slightly after the onset of the radio bursts. In this area, the detrended light curves for the 171A band show similar periodicity, with peaks lagging those seen in 211A. This is suggestive of rapid and impulsive cooling. NuSTAR x-rays provide evidence for a flare during the interval of Type III bursts but there is not a one to one correspondence between the x-rays and Type III bursts. Observations are somewhat consistent with previous studies showing correlated periodicities in 211A and Type II bursts, although periods are longer. Five minute periods have frequently been reported in sunspots

3:30 pm:
CESTA Seminar in 110 PAN
Speaker: Dr. Nicholas Propes and Dr. Zhiqiang Xing
Subject: A day in the Life of a Data Scientist at Seagate

What is it like being a Data Scientist at Seagate? Seagate Data Scientists Dr. Nicholas Propes and Dr. Zhiqiang Xing will talk about their job as a Data Scientist, the type of projects they work on, technical challenges they face and techniques they often employ to overcome technical challenges. They will also talk about upcoming trends and technologies in data science.


Wednesday, November 20th 2019
Speaker: Scott A. Chambers, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory
Subject: Extracting Quantitative Band-edge Profiles from Buried Heterojunctions from Hard X-ray Photoelectron Spectra

Semiconductor based devices are of broad, general importance, not only in electronics, but also in energy technology. In such devices, internal electric fields dictate the flow of charge that occurs both laterally and vertically. The associated potential profiles can be approximated from electronic transport data, and also calculated via Poisson-Schrodinger modeling, provided the properties of the constituent materials and interface structures are sufficiently well understood. These approaches work well for heterostructures involving, for instance, III-V semiconductors. However, when oxides are involved, such methods become unreliable because of poorly understood defects that can be present. There is, therefore, a critical need for new methods to enable the direct, experimental determination of band-edge profiles in heterojunctions involving these materials. In this lecture, I will demonstrate that hard x-ray photoelectron spectroscopy (HAXPES), interpreted by means of a newly developed algorithm, constitutes such a method. I will illustrate the power and utility of this approach with examples taken from the realm of epitaxial complex oxides on Group IV semiconductors [1-3] .
_______________
[1] Y. Du, P. V. Sushko, S. R. Spurgeon, M. E. Bowden, J. M. Ablett, T.-L. Lee, N. F. Quackenbush, J. C. Woicik, S. A. Chambers, Phys. Rev. Mater. 2, 094602 (2018).
[2] Z. H. Lim, N. F. Quackenbush, A. Penn, M. Chrysler, M. Bowden, Z. Zhu, J. M. Ablett, T.-L. Lee, J. M. LeBeau, J. C. Woicik, P. V. Sushko, S. A. Chambers, J. H. Ngai, Phys. Rev. Lett. 123, 026805 (2019).
[3] P. V. Sushko and S. A. Chambers, Sci. Rep., submitted (2019).

Faculty Host: Bharat Jalan
Speaker: Scott A. Chambers, Physical and Computational Sciences Directorate Pacific Northwest National Laboratory
Subject: Extracting Quantitative Band-edge Profiles from Buried Heterojunctions from Hard X-ray Photoelectron Spectra

Semiconductor based devices are of broad, general importance, not only in electronics, but also in energy technology. In such devices, internal electric fields dictate the flow of charge that occurs both laterally and vertically. The associated potential profiles can be approximated from electronic transport data, and also calculated via Poisson-Schrodinger modeling, provided the properties of the constituent materials and interface structures are sufficiently well understood. These approaches work well for heterostructures involving, for instance, III-V semiconductors. However, when oxides are involved, such methods become unreliable because of poorly understood defects that can be present. There is, therefore, a critical need for new methods to enable the direct, experimental determination of band-edge profiles in heterojunctions involving these materials. In this lecture, I will demonstrate that hard x-ray photoelectron spectroscopy (HAXPES), interpreted by means of a newly developed algorithm, constitutes such a method. I will illustrate the power and utility of this approach with examples taken from the realm of epitaxial complex oxides on Group IV semiconductors [1-3] .
_______________
[1] Y. Du, P. V. Sushko, S. R. Spurgeon, M. E. Bowden, J. M. Ablett, T.-L. Lee, N. F. Quackenbush, J. C. Woicik, S. A. Chambers, Phys. Rev. Mater. 2, 094602 (2018).
[2] Z. H. Lim, N. F. Quackenbush, A. Penn, M. Chrysler, M. Bowden, Z. Zhu, J. M. Ablett, T.-L. Lee, J. M. LeBeau, J. C. Woicik, P. V. Sushko, S. A. Chambers, J. H. Ngai, Phys. Rev. Lett. 123, 026805 (2019).
[3] P. V. Sushko and S. A. Chambers, Sci. Rep., submitted (2019).

Faculty Host: Bharat Jalan

Thursday, November 21st 2019
10:10 am:
Biophysics Seminar in 120 PAN
Speaker: TBA
12:10 pm:
Speaker: Evan Skillman and Liliya Williams
3:35 pm:
Speaker: Dimitar Sasselov, Harvard University
Subject: Stellar UV Light and the Origins of Life's Building Blocks

Evidence is emerging that mid-range UV light reaching the early Earth's surface might have played a central role in the synthesis and selection of life's molecular inventory. The process could be common to rocky Earth-size planets, and so spectroscopy of exoplanet atmospheres may help constrain it.

Faculty Host: Evan Skillman

Friday, November 22nd 2019
12:20 pm:
Speaker: Hsiu-Chung Yeh
Subject: Emptiness formation probability in Lieb-Liniger model.
Faculty Host: Boris Shklovskii
12:30 pm:
Speaker: Matheus Hostert
Subject: Have we seen new physics at short-baseline neutrino experiments?

Heavy neutral leptons are a well motivated extension of the Standard Model and offer a generic portal to hidden sectors. In this talk, I will discuss the latest ideas to search for heavy neutrinos and their exotic partners (e.g., hidden vector or scalar forces) at neutrino experiments. I will focus on scenarios that have been proposed to explain longstanding experimental anomalies, such as LSND and MiniBooNE, and show that most of these models are in fact ruled out by current data. Finally, I will highlight the prospects to test the remaining cases with near future experiments such as MicroBooNE.

2:30 pm:
No Colloquium. Physics Colloquium speaker Thurs: Dimitar Sasselov, Harvard University
4:40 pm:
Speaker: Vlad Pribiag
to be announced

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