High-order harmonic generations in tilted Weyl semimetals

TL;DR

This paper explores high-order harmonic generation in tilted Weyl semimetals, revealing unique noncentrosymmetrical signals, the influence of chemical potential, and the effects of Weyl cone tilting and chirality on harmonic responses.

Contribution

It provides a detailed analysis of HHGs in tilted Weyl semimetals, highlighting the role of electron pocket structure, chemical potential, and Weyl cone tilt in harmonic generation behaviors.

Findings

Strong noncentrosymmetrical high-order harmonics observed near type-II Weyl points.

Non-zero chemical potential enhances even-order harmonic generation.

Paired Weyl points with opposite chirality suppress overall even-order harmonics.

Abstract

We investigate high-order harmonic generations (HHGs) under the comparison of Weyl cones in two types. Due to the hyperboloidal electron pocket structure, strong noncentrosymmetrical generations in high orders are observed around a single type-II Weyl point, especially at frequency zero. Such remarkable DC signal is proved to have attributions from the intraband transition after spectral decomposition. Under weak pulse electric field , the linear optical response of a non-tilted Weyl cone is consistent with the Kubo theory. With more numerical simulations, we conclude the non-zero chemical potential can enhance the even-order generations, from the slightly tilted system to the over-tilted systems. In consideration of dynamical symmetries, type-I and -II Weyl cones also show different selective responses under the circularly polarized light. Finally, using a more realistic model containing two pairs of Weyl points, we demonstrate the paired Weyl points with opposite chirality could suppress the overall even-order generations.