Minimal model for chirally induced spin selectivity: spin-orbit coupling, tunneling and decoherence

Here we review a universal model for chirally induced spin-selectivity (CISS) as a standalone effect occurring in chiral molecules. We tie together the results of forward scattering in the gas phase to the results for photoelectrons in chiral self-assembled monolayers, and the more contemporary results in two terminal transport setups. We discuss the ingredients that are necessarily present in all experiments to date, which we identify as: (i) chirality, be it point, helical or configurational, (ii) the spin–orbit coupling as the spin active coupling of atomic origin, (iii) decoherence as a time-reversal symmetry breaking mechanism that avoids reciprocity relations in the linear regime and finally (iv) tunneling that accounts for the magnitude of the spin polarization effect. This proposal does not discard other mechanisms that can yield comparable spin effects related to interactions of the molecule to contacts or substrates that have been proposed but are less universal or apply to specific situations. Finally, we discuss recent results suggesting CISS as a molecular phenomenon in the realms of enantiomer selectivity, coherent electron transfer, and spin effects in chiroptical activity.