High-Harmonic Generation from Multi-Weyl Semimetals

In recent years high-order harmonic generation (HHG) has emerged as a unique technique not only to explore and diagnose topological phases of matter, but also to study the ultrafast dynamics in topological materials. Here we present theoretical investigations of HHG in multi-Weyl semimetals. We examine the influence of topological charge (or index), considering tight binding models with topological charges or Chern numbers of n = 1, 2, 3, and 4. We observe clear differences in the intensity yield of the harmonics generated by mid-infrared pulses interacting with multi-Weyl semimetals. We show that there is a substantial enhancement of HHG intensity in the case where the total emission comes from a system with topological charge of n = 2 in comparison to n = 1. For n = 3 and n = 4, we also find HHG intensity enhancement but less than that for the n = 2 case. In addition, we analyze the helicity and chirality dependence of the harmonics on the topological charge. We also study the helicity maps from this material system which provide the information about the chirality. Specifically, it is not only encoded in the large enhancement of the HHG signal for each harmonic order with the change in topological charge, but also in the right-handed and left-handed circularly polarized decompositions, if the driving laser is linearly polarized.