Olga Smirnova
In non-relativistic physics the concepts of geometry and topology are usually applied to characterize spatial structures, or structures in momentum space. We introduce the concept of temporal geometry [1], which encompasses geometric and topological properties of temporal shapes, e.g. trajectories traced by a tip of a time-dependent vector on sub-cycle time scale, and apply it to light-driven ultrafast electron currents in chiral molecules. The geometric concepts: curvature and connection emerge as ubiquitous features of photoexcited chiral electron dynamics opening a way to ultrafast, topologically non-trivial, enantio-sensitive chemical dynamics and new highly-sensitive robust chiral observables. The curvature and connection (i) rely on the interplay of molecular chirality and the polarization properties of light pulses, (ii) can be introduced for multiphoton processes, (iii) control enantio-sensitive geometric observables via non-equilibrium electronic dynamics excited by tailored laser fields and couple to spin bypassing magnetic interactions.
To demonstrate the link between the geometric fields and spin, we extend the concept of curvature to spin-resolved photoionization, and show that it is responsible for enantio-sensitive locking of the cation orientation to the photoelectron spin [2]. This translates into chirality induced spin selectivity in photoionization of oriented chiral molecules both in one photon and two-photon processes.
Finally, we show that an enantiosensitive current in the plane of polarization of light manifests itself as a spin polarization vortex, i.e., the spin vortex rotates in opposite direction for opposite enantiomers [3] reminiscent of Rashba effect in solids. This observable arises from the “coupling” of the geometric field to spin, and can lead to high spin polarization even for very small spin-orbit interaction. Our conclusions are illustrated for synthetic chiral matter. To quantify the link between chirality and spin-polarization in chiral targets, we construct chiral superpositions of electronic states in Argon and perform ab initio simulations of spin dynamics in photoionization using fully coupled spin-orbit code [4].
Our results provide a new perspective on the interplay of chirality and spin in photodynamics which does not rely on the interaction with the magnetic field component of light.
References:
[1] Geometry of temporal chiral structures I: The physical effects, A. F. Ordonez, A. Roos, P. Mayer, D.Ayuso, O. Smirnova, arXiv preprint arXiv:2409.02500v3, 2024
[2] Geometry of temporal chiral structures II: The formalism, arXiv preprint arXiv:2505.22744, 2025
[2] Spin-orientation locking in photoionization of chiral molecules, P. C. M. Flores, A.F. Ordonez, O. Smirnova arXiv preprint arXiv:2505.22433
[3] Enantio-sensitive spin polarization vortices in photoionization of chiral molecules by
circularly polarized light, P. C. M. Flores, S. Carlstroem, S. Patchkovskii, A. F. Ordonez, O. Smirnova, arXiv preprint arXiv:2505.23460
[4] General time dependent configuration interaction singles, S. Carlstroem et al, Phys. Rev. A 106, 2022, 042806