Determine the chirality of Weyl fermions from the circular dichroism spectra of time-dependent ARPES

TL;DR

This paper proposes a method to determine the chirality of Weyl fermions using circular dichroism in time-dependent ARPES spectra, supported by first-principles calculations for TaAs.

Contribution

It derives a direct relation between circular dichroism in time-dependent ARPES and Weyl fermion chirality, providing a new experimental approach.

Findings

Derived an expression linking CD in ARPES to Weyl fermion chirality

Proposed a method to determine chirality from CD spectra

Calculated CD spectra for TaAs from first principles

Abstract

We show that the intensity of pumped states near Weyl point is different when pumped with left- and right-handed circular polarized light, which leads to a special circular dichroism (CD) in time-dependent angle resolved photoemission spectra (ARPES). We derive the expression for the CD of time-dependent ARPES, which is directly related to the chirality of Weyl fermions. Based on the above derivation, we further propose a method to determine the chirality for a given Weyl point from the CD of time-dependent ARPES. The corresponding CD spectra for TaAs has then been calculated from the first principle, which can be compared with the future experiments.