Interpretation of chirality imprinted on photoelectron momentum spectra by three-dimensional light fields

Abstract

Synthetic three-dimensional (3D) light fields provide a new route to imprinting chirality on achiral matter through light--matter interaction. Although previous work has numerically demonstrated that chirality can be imprinted on the photoelectron momentum spectrum of atoms, a transparent analytical physical picture that links the structure of the driving field to the chirality of the spectrum is still an open question. Here, using frequency-domain theory based on nonperturbative quantum electrodynamics (QED), we demonstrate that this chirality originates from coherence between adjacent quantum transition channels. We further find that a symmetry transformation introduces into the coherence term a symmetry-breaking phase shift ($Φ_{\mathrm{SBPS}}$), which can be tuned by varying the laser-field parameters to preserve or break the corresponding symmetry in the spectrum. Once all such symmetries are broken, the momentum spectrum becomes chiral. In particular, for the noncollinear two-color 3D light field considered here, the spectrum is chiral for even $f=ω_2/ω_1$ and achiral for odd $f$. Our results provide a microscopic interpretation of chirality imprinting and establish a framework for predicting and controlling chiral electron wave packets with synthetic 3D light fields.