3:45–4:45 pm
GCIS W301/303 929 E 57th St.
When do Ultrafast Processes Matter? From Batteries to Strong Localization in Solar Materials
The Cushing lab focuses on ultrafast instrumentation science ranging from tabletop X-rays, to entangled photons, to new forms of battery spectroscopy. In this talk, I will briefly introduce our research areas, mentioning the increasingly “null” space explored with entangled photons, and then focus on two of the techniques—tabletop X-ray spectroscopy and ultrafast battery dynamics. For the latter, we use our newly developed, laser-driven ultrafast impedance method to investigate superionic conductors' many-body ion hopping mechanism. Picosecond temporal and spectral correlations differentiate electron-ion, phonon-ion, and potentially ion-ion interactions. Our first results on LLTO show that superionic conductivity does not occur by random thermal motion but rather by highly correlated ion-phonon modes in the THz, contrary to current ionic conductor design principles. Intriguingly, a meta-stable, increased ionic conductivity state that lasts 10 minutes after an ultrafast charge-transfer excitation is also measured. Next, we use transient X-ray techniques to explore the complex photodynamics of the Hubbard-Holstein Hamiltonian that describes systems ranging from solar fuel materials to O-LEDs. The ultrafast X-ray pulses measure a mix of electronic and structural dynamics and, using our excited state Bethe-Salpeter equation approach, we can extract time-resolved electron and hole energies, phonon and polaron modes, and transport phenomena. We measure materials with a range of electron-phonon coupling strength versus electronic correlations to map the Hubbard-Holstein phase space and evaluate its predictive accuracy for new excited state phenomena.
Speaker: Asst. Prof. Scott K. Cushing, CalTech, Dept. of Chemistry
Host: Prof. Greg Engel, Dept. of Chemistry (gsengel@uchicago.edu)
About the JFI Colloquium: The James Franck Institute Colloquium is a monthly event inviting distinguished scholars from research institutions around the globe to share creative, groundbreaking research at the intersection of chemistry, physics, and materials science. As an interdisciplinary institution, the JFI welcomes researchers and students from a wide variety of scientific disciplines to attend and partake in lively discussion. Colloquium speakers are nominated by JFI faculty and selected annually by the colloquium committee. Find the full calendar on the JFI website.