NSBP Innovate Seminar Series

 

The National Society of Black Physicists (NSBP) Innovate Seminar Series is a new forum for NSBP members to share their research ideas and projects in a non-specialist way with a wide audience. The 30-minute talk (followed by 15 minutes of Q&A) will be a Zoom Webinar, and recorded. It will be available to the whole world soon after the event at KITP Online.


Samantha O’Sullivan

Junior undergraduate student at Harvard University

Se diffusion into SrTiO3 substrate in monolayer FeSe/SrTiO3

Monolayer FeSe on a SrTiO3 (STO) substrate is a high-temperature superconductor with reported Tc as high as 100 K, but the mechanism for such enhanced Tc remains poorly understood. Samantha's research characterizes the atomic structural and chemical composition of the FeSe/STO interface using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). These measurements reveal the presence of selenium in the top layers of STO, located on interstitial sites and in the TiO2 layers. We support our measurement with density functional theory (DFT) calculations. We discuss implications of our findings on substrate-induced electron doping in the FeSe/STO heterostructure.

About the Speaker

Samantha O’Sullivan is a Junior undergraduate student at Harvard University concentrating in Physics and African-American Studies. She currently conducts research in experimental condensed matter physics at Harvard with a focus in electron microscopy of high temperature superconductors. She recently presented her research at the 2021 APS March Meeting and at NSBP's 2020 Annual Conference, where she won the award for "Best Talk in Condensed Matter". Outside of condensed matter Samantha is interested in plasma physics, and she will join Princeton's Plasma Physics Laboratory this summer to investigate tokamak edge physics. In her free time, Samantha enjoys genealogy research, running, and poetry.


Monday, March 29 at 5:30 PM EDT

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Carl E. Fields

Department of Physics & Astronomy at Michigan State University

Next-Generation Simulations of The Remarkable Deaths of Massive Stars

Core-collapse supernova explosions (CCSN) are one possible fate of a massive star. Simulations of CCSNe rely on the properties of the massive star at core-collapse. As such, a critical component is the realization of realistic initial conditions. Multidimensional progenitor models can enable us to capture the chaotic nuclear shell burning occurring deep within the stellar interior. I will discuss ongoing efforts to progress our understanding of the nature of massive stars through next-generation hydrodynamic stellar models. In particular, I will present recent results of three-dimensional hydrodynamic models of massive stars evolved for the final moments before collapse. These recent results suggest that realistic 3D progenitor models can be favorable for obtaining robust models of CCSN explosions and are an important aspect of massive star explosions that must be taken into consideration. I will conclude with a brief discussion of the implications our models have for predication of multi-messenger signals from CCSNe.

About the Speaker

Carl E. Fields is a Ph.D. Candidate in the Department of Physics & Astronomy at Michigan State University working with Prof. Sean Couch. Carl's research focusses on astrophysical sources of gravitational waves, stellar nucleosynthesis, and multi-dimensional simulations of core-collapse supernova explosions and their massive star progenitors. Carl is jointly supported by the National Science Foundation and Los Alamos National Laboratory. Carl received his undergraduate degrees in Physics and Earth & Space Exploration (Astrophysics) where he worked with Prof. Frank Timmes. In 2020, Fields was award the Price Prize by Ohio State University and named to the Forbes 2021 Class of 30 under 30 for Science.


Wednesday, January 27 at 5:30 PM EST

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Dr. Carol Y. Scarlett

Assistant Professor, Department of Physics at Florida A&M University

Axionic Dark Matter – New Search Techniques

It is well known that a light, pseudo-scalar particle called the Axion can solve several fundamental physics problems. Proposed to explain the lack of a neutron EDM, such a weakly interacting particle has the right characteristics to explain formation of galaxies, by providing the needed mass in the form of Cold Dark Matter. Additionally, there has been data collected on the decay of several radioactive nuclei suggesting the need for weakly interacting particles streaming from the sun and throughout the galaxy. This talk will review the theory behind axion particles, examples of early experimental searches and some new search techniques. The nuclei data reviewed here can provide complimentary results to any existing axion searches as well as a novel type of search that can be conducted.

About the Speaker

Dr. Carol Scarlett is an assistant professor of physics at Florida A&M University. She is involved in dark matter research as well as developing a program to use positrons to study plasmas and weak interactions. Her research group is also involved with a measure of the weak interaction cross section for a positron on a neutron.


Tuesday, November 24 at 5:30 PM EST

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Dr. Charles Brown

Postdoctoral scholar and Ford Foundation fellow at the University of California, Berkeley

Interacting Bosons in the Flat Band of an Optical Kagome Lattice

Geometric frustration of particle motion in a kagome lattice causes the single-particle band structure to exhibit a dispersion-less, flat band. Generally, frustration can cause a vast degeneracy of low-energy states, and instabilities in the presence of atomic interactions may lead to the manifestation of exotic states of matter. The kagome lattice, a pattern of vertex-sharing triangular plaquettes, offers the highest degree of frustration among two-dimensional lattice geometries. We create an optical kagome lattice by superimposing two optical triangular lattices made from laser light with commensurate wavelengths. We probe the band structure of the kagome lattice by preparing a Bose-Einstein condensate in excited Bloch states of the lattice, and then measuring the atoms’ group velocity via the atomic momentum distribution. We find that atomic interactions renormalize the kagome lattice band structure, significantly increasing the dispersion of the third band, which, according to non-interacting band theory, should be nearly flat (dispersion-less). Measurements at various lattice depths and gas densities agree quantitatively with predictions from the lattice Gross-Pitaevskii equation, which indicates that the observed band structure distortion, onset by atomic interactions, is caused by the distortion of the overall lattice potential away from the kagome geometry.
[+] https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.133001.
[+] https://arxiv.org/abs/2007.05928.

About the Speaker

Dr. Charles Brown is an experimental quantum physicist, science communicator, and champion for increased Black American representation in physics. Charles earned his B.S. with honors in physics at the University of Minnesota, Twin Cities. He also earned a Ph.D. in physics at Yale University, where he conducted experiments with superfluid helium-filled optical cavities, and magnetically levitated superfluid helium drops in vacuum. He is now a postdoctoral scholar and Ford Foundation fellow at the University of California, Berkeley. At Berkeley, he is a member of the Ultracold Atomic Physics Group, where he investigates ultracold atoms trapped in optical lattices, which offers an avenue to study a rich variety of many-body quantum physics phenomena. Charles has a long history of both empowering students - spanning the elementary through graduate levels - to pursue their STEM interests, and advocating for the interests of Black students. Charles recently wrote a widely read op-ed about Black underrepresentation in physics that appeared in Physics Today, which has been sparking important conversations regarding necessary changes in the physics community.


Tuesday, September 29 at 5:30 PM EST

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Prof. Philip Phillips

Professor, University of Illinois at Urbana-Champaign

Beyond BCS Theory: Exact Model for Superconductivity and Mottness

High-temperature superconductivity in the cuprates remains an unsolved problem because the cuprates start off their lives as Mott insulators in which no organizing principle such a Fermi surface can be invoked to treat the electron interactions. Consequently, it would be advantageous to solve even a toy model that exhibits both Mottness and superconductivity. In 1992 Hatsugai and Khomoto wrote down a momentum-space model for a Mott insulator which is safe to say was largely overlooked, their paper garnering just 21 citations (6 due to our group). I will show exactly[1] that this model when appended with a weak pairing interaction exhibits not only the analogue of Cooper's instability but also a superconducting ground state, thereby demonstrating that a model for a doped Mott insulator can exhibit superconductivity. The properties of the superconducting state differ drastically from that of the standard BCS theory. The elementary excitations of this superconductor are not linear combinations of particle and hole states but rather superpositions of doublons and holons, composite excitations signaling that the superconducting ground state of the doped Mott insulator inherits the non-Fermi liquid character of the normal state. Additional unexpected features of this model are that it exhibits a superconductivity-induced transfer of spectral weight from high to low energies and a suppression of the superfluid density as seen in the cuprates.
[1] https://www.nature.com/articles/s41567-020-0988-4.

About the Speaker

Professor Philip Phillips received his bachelor's degree from Walla Walla College in 1979, and his Ph.D. from the University of Washington in 1982. After a Miller Fellowship at Berkeley, he joined the faculty at Massachusetts Institute of Technology (1984-1993). Professor Phillips came to the University of Illinois in 1993. Professor Phillips is a theoretical condensed matter physicist who has an international reputation for his work on transport in disordered and strongly correlated low-dimensional systems. He is the inventor of various models for Bose metals, Mottness, and the random dimer model, which exhibits extended states in one dimension, thereby representing an exception to the localization theorem of Anderson's.


Thursday, August 27 at 5:30 PM EST

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Delilah Gates

Ph.D candidate at Harvard University Physics and member of the Center for the Black Hole Initiative

Observable Blueshift from Circular Equatorial Orbiters around Kerr Black Holes

With the success of the Event Horizon Telescope, identifying new observational signatures of black holes are of increasing interest. In this talk we investigate blueshift of photons from an equatorial accretion disk of emitters orbiting on stable circular orbits terminating at the ISCO.
We analytically calculate the blueshift of photons that escape to the celestial sphere (instead of falling into the black hole) and numerically calculate the maximum blueshift received by an observer at fixed angle on the celestial sphere.

About the Speaker

Delilah Gates is a graduate student in Prof. Andrew Strominger’s group studying observational signatures of high-spin black holes and near-horizon near extreme limits related to the emergent near-horizon conformal symmetry of the Kerr black hole solution.


Tuesday, July 21 at 1:00 PM EST

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