Non-linear optical response and HHG in 3D Dirac semimetals

Attosecond-duration pulses of extreme ultraviolet to X-ray light, generated via high harmonic generation (HHG), have proven to be highly useful tools in the study of the smallest and quickest fundamental phenomena. The study of HHG in condensed matter systems has attracted much interest due to its potential to realize novel solid-state optical technologies, as well as greater brightnesses compared to gas-phase HHG. We will present results on high harmonic generation in topological materials like 3D Dirac and Weyl semimetals, which exhibit strong, non-linear response to incident fields, which result in efficient generation of odd harmonics. We consider the massless Dirac quasiparticle limit, previously used to predict the harmonic spectra of 2D graphene due to its simplicity and physical transparency, and extend it to 3D Dirac semimetals. We study its non-linear response due to incident fields, and predict its harmonic spectra. A comparison of our results with graphene as well as potential novel photonic applications will be discussed.