Meet Dr. Geoffrey Diederich

Geoffrey Diederich

Dr. Geoffrey Diederich

Advisor: Dr. Xiaodong Xu

Institution: University of Washington 

Bio:  Geoffrey Diederich received their bachelor’s of science in physics, with minors in chemistry and mathematics, in 2009 from Bowling Green State University. In 2012, they received a Masters of Science from the same institution for research on the synthesis and implementation of colloidal quantum dots under Dr. Mikhail Zamkov. They then began their Ph.D. at the University of Denver under the supervision of Dr. Mark Siemens where they studied multidimensional coherent spectroscopy (MDCS), an ultrafast spectroscopy that probes excited stated dynamics in a more comprehensive way than typical pump-probe experiments. During this time, they improved the experimental implementation of MDCS, making the retrieval of the coherent information more intuitive, expanded the understanding of the information in the data by implementing new techniques for lineshape analysis, and studied the ultrafast dynamics of perovskite solar devices. They are currently the recipient of the ORISE IC Community Postdoctoral Fellowship, working at the University of Washington under Dr. Xiaodong Xu. Their current research aims to explore the ultrafast dynamics of the novel physics presented in 2D materials. Specifically, they are interested in the interaction of intense light pulses with the magnetic states in the newly discovered 2D magnets, and how these interactions could lead to coherent control schemes that allow for magnetic switching on the femtosecond timescale.

Abstract:  My work is concerned with the measurement and control of novel quantum phenomena at the femtosecond timescales. To accomplish this, I use ultrafast laser pulses to excite materials and then interrogate their reaction to that excitation. Currently, I am studying how the fragile quantum states present in topological insulators, few monolayer magnets, unconventional superconductors, and Moire materials react to these intense pulses. The coherent nature of the laser pulses allows us to launch coherent excitations of magnetic symmetry breaking (magnons), lattice distortions (phonons), and bound excited charge carriers (excitons) which can then interact to create a complex, fascinating, and dynamic system that cannot be measured by steady-state techniques. Measurement of these excitations then allows us to vary external experimental parameters, such as applied electric and magnetic fields, to control their interaction, allowing us a knob to tune the material response to the desired outcome. Given the intense electromagnetic fields present in ultrafast laser pulses, we can then remove the externally applied fields and use the light fields to tune the material response and the femtosecond timescale. A short list of our findings to date has been the observation of acoustic frequency comb generation in an iron pnictide material, anomalous symmetry in the magnetic topological insulator MnBi2Te4, and strong magnon-phonon coupling in the 2D magnet CrSBr.