Sub-cycle resolved strong field ionization of chiral molecules and the origin of chiral photoelectron asymmetries

We report on strong field ionization of S- and R-propylene oxide in circularly polarized two-color laser fields. We find that the relative helicity of the two single color laser fields affects the photoelectron circular dichroism (PECD). Further, we observe that PECD is modulated as a function of the sub-cycle release time of the electron. Our experimental observations are successfully described by a heuristic model based on electrons in chiral initial states, which are selectively liberated by the laser field and, after tunneling, interact with an achiral Coulomb potential.