Department of Physics

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 [1]. 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 [2]. 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 [3] and topological insulators [4].

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.

Selected Publications:

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