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Nonlinear optics has recently emerged as an attractive approach for both probing topological properties and driving topological materials into new states. Here, I will describe our use of
ultrafast nonlinear optics to study topological semimetals. I will primarily focus on the Weyl semimetal TaAs, in which we used THz emission spectroscopy was used to provide new insight into the circular photogalvanic effect, ultrafast X-ray diffraction to directly observe coherent
longitudinal and shear phonons, and time-resolved second harmonic generation (SHG) to reveal a photoinduced transient symmetry breaking phase. I will also briefly describe our recent SHG measurements on the polar semiconductor BiTeBr as well as high harmonic generation
measurements on the chiral topological semimetals CoSi and RhSi. Overall, our studies demonstrate the utility of nonlinear optics in shedding new light on the properties of topological
materials. |