Pulse-duration-sensitive high harmonics and attosecond locally-chiral light from a chiral topological Weyl semimetal

TL;DR

This paper demonstrates how pulse duration influences high harmonic generation in chiral Weyl semimetals, enabling the creation of attosecond locally chiral light with potential applications in topological electronics.

Contribution

It reveals the role of pulse duration in extending HHG to higher energies and elucidates selection rules for generating chiral attosecond light in Weyl semimetals.

Findings

Pulse duration promotes higher conduction band excitations in HHG.

Chiral Weyl semimetals enable asymmetric local electric fields on attosecond timescales.

Pronounced circular dichroism depends on laser helicity and crystal handedness.

Abstract

High harmonic generation (HHG) in solids results from an interplay between intraband acceleration and electron-hole recombination driven by a high-intensity laser pulse. Here, we theoretically reveal that the driving pulse duration can play a major role in extending HHG to higher photon energies by promoting higher conduction band excitations. The effect is present in a conventional semiconductor as Si, restricted in a large-gap insulator as MgO, and most prominent in RhSi, a prototypical chiral Weyl semimetal presenting numerous band crossings. Further, we elucidate the HHG selection rules in RhSi required for the synthesis of attosecond locally chiral light. The chiral crystal structure enables the generation of a local 3D electric field exhibiting an asymmetric instantaneous torsion on attosecond timescales. A pronounced circular dichroism emerges when the driving helicity is either aligned with or opposite to the crystal handedness. Our findings motivate future experiments in chiral Weyl semimetals to track high-energy band crossings and in-situ locally chiral light, paving the way for chiral compact light sources and light-wave driven topological electronics.