A theoretical account of why the chiral induced spin selectivity (CISS) effect arises. It establishes two jointly necessary conditions: (1) molecular chirality is required to break spin degeneracy in structures lacking heavy elements, where spin-orbit coupling alone is too weak; and (2) dissipation (coupling to an environment) is indispensable for the molecule to develop a non-vanishing steady-state spin polarization. Only when both are coordinated does a spin-polarized current emerge, resolving why coherent, dissipationless models fail to reproduce CISS.
A theoretical study of the origin of the chiral induced spin selectivity (CISS) effect, in which electrons flowing through a chiral molecule become spin-polarized along their direction of propagation…