Enantiosensitive molecular compass

TL;DR

This paper uncovers a universal electric-dipole mechanism in chiral molecules that explains spin-selective photoionization, providing insights into the fundamental origin of the CISS effect and its relation to molecular geometry.

Contribution

It introduces a new chiral molecular compass mechanism based on electric-dipole interactions that explains spin selectivity in photoionization without requiring magnetic fields.

Findings

Discovered a universal electric-dipole mechanism for spin selectivity.

Demonstrated spin-orientation locking to molecular geometry in chiral molecules.

Showed that achiral molecules cannot sustain time-odd correlations.

Abstract

Chirality describes the asymmetry between an object and its mirror image and manifests itself in diverse functionalities across all scales of matter - from molecules and aggregates to thin films and bulk chiral materials. A particularly intriguing example is chirality-induced spin selectivity (CISS), where chiral structures orient electron spins enantio-sensitively. Despite extensive research, the fundamental origin of spin-chirality coupling, the unexpectedly large magnitude of the CISS effect, and the possible role of electromagnetic fields in it remain unclear. Here, we address these issues by examining the simplest scenario: spin-resolved photoionization of randomly oriented chiral molecules. We uncover a universal mechanism of spin-selective chiral photodynamics, arising solely from electric-dipole interactions and previously unrecognized. This mechanism embodies a chiral molecular compass - a photoinduced magnetization vector that orients the photoelectron spin. It arises in photoexcited chiral molecules even under isotropic illumination, operates even in isotropic chiral media, and enables a phenomenon central to CISS: locking of the photoelectron spin orientation to molecular geometry. It shows that chiral molecules can sustain time-odd correlations whereas achiral molecules cannot. Our findings have broad implications, from unambiguously identifying the origin of CISS effect in photoionization to harvesting correlations underlying this effect in other forms of CISS in various chiral materials.