Abstract:

The transport of electrons and ions is just as critical as their generation in quantum and energy materials. Atomic motion and electronic response to a moving charge can hinder or accelerate transport. Interfaces and defects do the same. How can we tune these interactions to improve charge transport? We design and apply a range of custom-built spectroscopic approaches to measure electron-lattice and ion-lattice interactions from ultrafast timescales to nanometer length scales. We aim to understand how the atomic lattice can be designed to promote rather than hinder transport. In solid electrolytes, we identify vibrational modes that promote transport, revealing design routes to superionic transport. This includes progress towards measuring ultrafast ion hopping across and within grain boundaries.  In photoexcited iron oxides, we tune the competition between lattice and electronic localization to suppress polaron formation in an otherwise polaron-limited class of materials. We then use photomodulated TEM-EELS to track how photoexcited carriers accumulate at surfaces or defects, completing the picture. The lessons and instrumentation developed here open new opportunities for studies in organic ion conductors, hydrated membranes, and quantum materials.

Bio:
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 Moore, DOE, AFOSR, Cottrell, Sloan, DARPA, and related awards. Scott has published over 90 papers that have been cited more than12,000 times. Scott holds multiple patents, some of which have led to startups, including his recent co-founding of Quantelix.