Vibrationally Mediated Dzyaloshinskii-Moriya Interaction as the Origin of Chirality-Induced Spin Selectivity in Donor–Acceptor Molecules

Chirality-induced spin selectivity (CISS) was recently observed in photoexcited donor-chiral bridge-acceptor molecules, but a predictive theory able to explain available experiments is still lacking. Here, we show that torsional modes modulating hopping and spin-orbit coupling give rise to a Dzyaloshinskii-Moriya interaction between the transferred electron and the one sitting on the donor, producing high spin polarization for realistic parameters. Our model introduces a low-energy scale in the spin dynamics that explains the magnetic field dependence observed in EPR measurements and predicts a nontrivial temperature dependence, as demonstrated by numerical simulations. The present theory lays the foundations for future test bed experiments and for the design of applications in spintronics and quantum technologies.