The Physics and Astronomy colloquium is a forum for invited scientists to present modern research in a fashion accessible to those with a background in physics, but who are not experts in the field. Talks are aimed at a graduate level.
The colloquium is held most Thursdays during the Fall and Spring semesters at 3:45 pm in NH 170, unless otherwise indicated.
If you have questions about our colloquia, please contact Bruno Uchoa at email@example.com.
Host: Joseph Tischler
Title: "Towards Non-Blinking Strongly Confined Perovskite Quantum Dots"
Abstract: Quantum information science has shown its capabilities to enable secure quantum communications. Single photon emitters that emit photons one at a time are fundamental elements of such transformative technologies. Colloidal cesium lead halide (CsPbX3, X=Br, I) perovskite quantum dots are ideal for next-generation single photon emitters because of their high room-temperature luminescence efficiency and low-cost, scalable syntheses. Unfortunately, individual perovskite quantum dots show insufficient photostability and severe photoluminescence intensity fluctuations (also called blinking). One major roadblock toward non-blinking, photostable perovskite quantum dots is their highly ionic crystal structure. When preparing single perovskite quantum dot samples, quantum dot colloids often need to be diluted. During this process ligands can detach from the quantum dot, introducing defects. This is particularly detrimental to strongly confined perovskite quantum dots since exciton-surface lattice interaction is greatly enhanced.
To suppress perovskite quantum dot blinking and photodegradation, we embedded quantum dots in an organic crystal matrix consisting of Phenethylammonium bromide (PEABr) salts. The bromide rich surface of a quantum dot can be epitaxially anchored onto the PEABr crystals and therefore be stabilized. Individual strongly confined CsPbBr3 quantum dots in our matrix show nearly non-blinking behavior under non-resonant laser excitations at room temperature. These quantum dots remain photostable without photoluminescence intensity decrease and spectral shift after more than 12 hours of continued excitations. We anticipate that those quantum dots will lead to more accurate and detailed study of exciton dynamics and structural-optical property relationships in this important class of materials.
Host: Brad Abbott
Title: "Computing for Large High Energy Physics Experiments with a Focus on CMS"
Abstract: Computing is necessary for high energy experiments. Data collected from experiments grows year to year until it is too large to fit on one singular machine, and those single machines cannot handle the computation required to perform analysis on this data. In order to do analysis at this massive scale we can use a grid system that stores the data on disks. A grid system is working to network computers in a flexible and scalable architecture. Instead of one computer we are now connecting two and then three and then as many as we can. We also want to be able to archive the data and we do that through a tape system. In this talk we explore how we not only use grid systems, but also how data is stored.
Host: Sean Matt
Title: "Young Protostellar Disks and Their Asymmetric Environments Set the Stage for Planet Formation"
Abstract: Evidence that planet formation begins when protostars are less than 1 million years old continues to build. During this early phase of star formation, protostars and their disks are still embedded in (and feeding from) their natal environments at a time when I have demonstrated that the first steps of planet formation occur. In particular, streamers---long and narrow infalling channels that funnel material to disks from their environments---have been predicted theoretically and serendipitously observed in a variety of tracers. In this talk I will outline the various ways streamers can influence the star and planet formation process and describe my current research and plans to probe how asymmetric infall from the larger-scale environment influence disk structure, temperature, and chemistry. These disk properties are directly connected to when planets form, where, and with what composition. Despite the growing evidence that the larger scale environments have an influence on the youngest planet-forming disks, my PRODIGE survey, carried out with the NOEMA interferometer, is the first and only large observing program specifically designed with streamers in mind. Results from my observations with the PRODIGE survey pave the way for more-detailed observations targeting the initial conditions of planet formation.
Host: Sean Matt
Title: "Galactic Archaeology: the Formation and Evolution of the Milky Way"
Abstract: Our understanding of the Milky Way is in the midst of a revolution through the combination of large-scale spectroscopic surveys such as APOGEE and GALAH along with the Gaia satellite providing information on billions of stars across the Galaxy. I will give an overview of the current chemodynamic structure of the Milky Way from these surveys, ranging from the bulge to the edge of the disk, and outline the key physical processes that have governed the evolution of our Galaxy. I will describe our state-of-the-art chemical evolution models, which are the first to be able to match the detailed chemical structure across the Milky Way. I will also demonstrate how the Milky Way can be used as a benchmark for galaxy evolution, outlining a new technique that enables direct comparisons of our Galaxy to external galaxies for the first time. I will highlight future applications of these analysis techniques, including to our upcoming large ESO-MUSE program GECKOS. GECKOS will deliver MUSE observations of 35 edge-on galaxies with unprecedented depth and spatial coverage, providing detailed kinematic and stellar population measurements beyond the equivalent of the solar neighborhood in these galaxies.