Light-driven out-of-equilibrium phenomena in solids: ultrafast spectroscopy of topology, Floquet phases of matter, and magnetism

events hall

Dr. Ofer Neufeld


David Wang Auditorium, 3rd floor Dalia Meidan Bldg.


In recent years highly nonlinear optics has paved the way to novel material spectroscopies such as all-optical band-structure reconstruction, probing exciton formation and recombination in real-time, and tracking ultrafast phase transitions (both structural and electronic). In this approach, intense laser pulses irradiate a sample, triggering non-perturbative responses such as high harmonic generation (HHG), photoionization, etc.; which can be analyzed to obtain information about the sample and out-of-equilibrium dynamics occurring within it. However, in order to extract information from spectra, one requires a deep understanding of the mechanisms generating the response (i.e. connecting microscopic structure to observables), and a proper comparison between theory and experiment. I will discuss this fundamental issue in the context of ab-initio methodologies and present our recent work on probing material topology with HHG, and Floquet light-driven phases of matter with photoelectrons. I will show that material topology is not imprinted onto spectra in a straightforward manner, and that its typical contribution to HHG is rather weak, contrary to the common conception in the field. On the other hand, I will show that Floquet phases of matter can be probed very effectively with photoelectrons and are expected to strongly affect ultrafast material responses. Lastly, I’ll show that strong-field laser irradiation allows inducing, and probing, attosecond magnetic responses, which are the fastest magnetic responses predicted to date.

Host: Prof. Eugen Rabkin