Shambhu Ghimire

My research interests are in ultrafast condensed matter, atomic, molecular and optical physics. Currently, we are studying extremely non-linear optical response of quantum materials such as two-dimensional crystals, topological insulators and Weyl semi-metals. Here, the strength of laser field is often comparable to the binding strengths of the material, therefore the typical approximations of nonlinear optics breakdown spectacularly. In 2010, our group discovered that materials subjected to such strong fields produce high-order harmonics of driving laser. In the first experiment, we observed high-harmonics up to 25th orders from zinc oxide crystals subjected to intense mid-infrared laser. Since then there has been a lot of exciting work in the field, which includes understanding the microscopic mechanism of high-harmonic generation and using it to probe materials properties. Some of the properties this scheme can probe are valence charge distributions, electronic band structure, Berry curvature, and quantum mechanical phase transitions including topological phase transitions.

[2024] Ultrafast high-harmonic spectroscopy of solids, Nature Physics [2023] Giant room-temperature nonlinearities in a monolayer Janus topological semiconductor., Nature communications [2023] High-harmonic generation from artificially stacked 2D crystals, NANOPHOTONICS [2023] Floquet engineering of strongly driven excitons in monolayer tungsten disulfide, NATURE PHYSICS