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Events on Thursday, December 7th, 2023

R. G. Herb Condensed Matter Seminar
Inducing non-equilibrium phases in semiconductors with time-periodic drives
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Ilya Esin, Caltech
Abstract: “Floquet engineering” - designing band structures “on-demand" through an application of coherent time-periodic drives, has recently emerged as a powerful tool for inducing exotic phenomena in ordinary materials. In this talk, I will discuss the application of Floquet engineering for inducing novel non-equilibrium phases of matter in steady states of time-periodically driven semiconductors. The steady states are achieved due to the interplay between the coherent external drive, electron-electron interactions, and dissipative processes arising from the coupling to phonons and the electromagnetic environment. I will show that despite the highly non-equilibrium nature of these systems, by judicially choosing the properties of the material, the external drive, and the environments, their steady states can exhibit topological transport and strongly correlated phases such as a novel electronic liquid gyro-crystalline phase.
Host: Ilya Esterlis
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Astronomy Colloquium
Decoding Exoplanet Atmospheres: The Revolutionary Role of JWST
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Luis Welbanks, Arizona State University
Abstract: The 2020s and beyond will be the era of spectroscopy of exoplanet atmospheres. In just 2 years, our field has made dramatic advancements, moving from having very limited wavelength coverage and precision data from the Hubble Space Telescope (HST), to having high-precision spectroscopy over a wide wavelength range (~0.4 to 20μm) with the James Webb Space Telescope (JWST). These exquisite observations come with the opportunity to perform detailed reconnaissance of exoplanet atmospheres, explore their chemical and physical properties, and perform population-level studies to test our hypotheses for planet formation and evolution.

In this talk, I will share with you the advancements ushered by the era of JWST, allowing us to answer not only what exoplanet atmospheres are made of, but also which data drive our inferences and how reliable these inferences are. I will present the results from several programs with JWST. In these programs, we detect and constrain several chemical species that were previously elusive in exoplanetary atmospheres, including methane (CH4), ammonia (NH3), sulfur dioxide (SO2), carbon monoxide (CO), and carbon dioxide (CO2), alongside several precise water (H2O) measurements. The atmospheric retrievals performed on these data provide insights into the dynamics, chemistry, and climatic conditions of these distant worlds, as well as their metallicities. They also provide the relative elemental ratios (C/O, N/O, N/S) necessary to better understand the formation and evolution pathways of planetary systems.

I will present our progress in robustly and accurately processing JWST Time-Series Observations data. Additionally, I'll discuss modeling advancements and our methods for reliably inferring the complete chemical inventory of our diverse exoplanet sample. Our findings underscore the transformative power of JWST and pave the way for future, in-depth atmospheric investigations of a larger exoplanet population.
Host: Ke Zhang
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