High harmonic generation from electrons moving in topological spin textures

TL;DR

This paper explores how topological spin textures influence high harmonic generation (HHG) in electrons, revealing that geometrical properties like Berry curvature significantly affect HHG signals, especially under low-frequency optical excitation.

Contribution

It demonstrates that scalar chirality in topological spin textures can control HHG responses through geometrical effects, highlighting the role of Berry curvature in electron dynamics.

Findings

Scalar chirality sign change affects longitudinal HHG response.

Berry curvature influences HHG even when energy band structure remains unchanged.

Interband currents modulated by anomalous velocity contribute to HHG signals.

Abstract

High harmonic generation (HHG) is a striking phenomenon, which reflects the ultrafast dynamics of electrons. Recently, it has been demonstrated that HHG can be used to reconstruct not only the energy band structure but also the geometric structure characterized by the Berry curvature. Here, we numerically investigate HHG arising from electrons coupled with a topological spin texture in a spin scalar chiral state where time reversal symmetry is broken. In this system, a sign change in scalar chirality alters the sign of the Berry curvature while keeping the energy band structure unchanged, allowing us to discuss purely geometrical effects on HHG. Notably, we found that, when the optical frequency is significantly lower than the energy gap, the sign of scalar chirality largely affects the longitudinal response parallel to the optical field rather than the transverse response. Our analysis suggests that this can be attributed to interband currents induced by the recombination of electron-hole pairs whose real-space trajectories are modulated by the anomalous velocity term.