About the Seminar:

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. Reducing charge density on the apical O anion using a transient charge-transfer transition also improves ionic conductivity on the picosecond timescale of optical phonons. 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 and spin correlations to map the Hubbard-Holstein Hamiltonian phase space and evaluate its predictive accuracy for new excited state materials design.

About the Speaker:

Scott Cushing is an Assistant Professor at Caltech with a multidisciplinary background spanning Chemistry, Materials Science, and Physics. His research focuses on creating new scientific instrumentation to translate quantum and ultrafast phenomena into practical devices. The Cushing lab is currently pioneering the use of ultrafast X-rays, electrons, and entangled photons for a range of microscopy and spectroscopy applications. Scott has been awarded DOE, AFOSR, Rose Hill, Cottrell, W.M. Keck, DARPA, and ACS-related Early Career awards. Scott has published over 70 papers that have been cited >10,000 times.  Scott holds multiple patents, some of which have led to start-up companies.