Electron dynamics inside molecules or materials occur in ultrafast timescales, therefore, they are too fast for conventional spectroscopic methods. Those dynamics, particularly in quantum materials such as two-dimensional (2D) crystals and topological insulators, have potential applications in modern technologies such as spintronics and fault-tolerant quantum computing. This lecture introduces a novel spectroscopic approach that has the potential to access natural timescales of electrons. It is based on the mechanism for high-order harmonic generation (HHG) in materials subjected to intense laser pulses. While the atomic HHG process has been studied since the late eighties the experimental realization of solid-state HHG was just about a decade ago . Since then, there has been rapidly growing interest in investigating the solid-state HHG process, focusing on similarities and differences to their atomic cousins, and subsequently exploring its potential as an ultrafast probe of structure and dynamics in materials . Just within a decade, solid-state HHG has emerged as one of the frontiers of attosecond science, with the latest splash on quantum materials. In this talk, I will give a brief overview of this emerging field and present our latest results in atomically thin 2D-crystals  and topological insulators .
Dr. Shambhu Ghimire is a Lead Scientist and a Principal Investigator at the Stanford PULSE Institute, SLAC National Accelerator Laboratory. He is a recipient of the prestigious Young Investigator award from the U.S. Department of Energy (2014-2019). His research interests are on Attosecond Science and Nonlinear Optics. He received a Ph.D. degree in physics from Kansas State University in 2007 and a postdoctoral training from University of Michigan before joining SLAC in 2009.
1. S. Ghimire et al., Observation of high-order harmonics in a bulk crystal, Nature Physics 7, 2, 138 (2011)
2. S. Ghimire and D. Reis, Review: High-order harmonic generation from solids, Nature Physics 15, 10-16 (2019)
3. H. Liu et al, High-harmonic generation in atomically thin semiconductor, Nature Physics 13, 262-265 (2017)
4. D. Baykusheva et al., All-optical probe of three-dimensional topological insulators based on high-harmonic generation by circularly polarized laser fields, Nano Lett. Oct. 22, 2021