Quantum materials such as topological insulators, Weyl-semimetals, and atomically thin two-dimensional crystals have intriguing electronic properties, which makes them promising candidates for their potential applications in next-generation technology. Therefore, it is desirable to investigate the electronic properties of these materials, perhaps through various methods such that their full potential, as well as the limitations, can be identified. In this talk, I will introduce a novel spectroscopic approach based on the use of strong ultrafast laser pulses and the generation of high-order harmonics. Analysis of temporal and spectral properties of high-order harmonics from these materials reveals their valence charge density distributions, electronic band-structure, topology, as well as driven electron dynamics in the natural time scales of electrons. The advantages of this approach over conventional methods include the use of the all-optical setting, no physical contacts to samples, and much of the measurements that can be performed in ambient conditions. More importantly, the non-perturbative interaction to strong laser pulses forms novel quantum phases, which could be probed by analyzing high-order harmonics.
Short Bio: Dr. Shambhu Ghimire is a Staff Scientist at Stanford PULSE Institute, where he leads Attosecond X-ray Photonics Group. He is a recipient of the prestigious Young Investigator award from U.S. Department of Energy. His research interests are on Strong-field Physics and Nonlinear X-ray Science. He received his Ph.D. in physics from Kansas State University in 2007 and went to University of Michigan for a post-doc job before he joined Stanford in 2009.
- J. Lu, E. Cunningham, Y. S. You, D. A. Reis and S. Ghimire, Interferometry of dipole phase in high harmonics from solids, Nature Photonics 13, 96100 (2019)
- S. Ghimire and D. Reis, Review: High-order harmonic generation from solids, Nature Physics Online November (2018).
- Y. You, Y. Yin, Y. Wu, A. Chew, X. Ren, F. Zhuang, S. Gholam-Mirzaei, M. Chini, Z. Chang and S. Ghimire, High-harmonic generation in amorphous solids, Nature Comm 8, 724 (2017)
- Y. You, D. Reis and S. Ghimire, Anisotropic high-harmonic generation in bulk crystals, Nature Physics, 13, 345-349 (2017).
- N. Ddabashimiye, S. Ghimire, M. Wu, D Browne, K. Schafer, M. Gaarde and D. Reis, Solid-state harmonics beyond atomic limit, Nature 534, 520-523 (2016).