  Chiral-induced spin selectivity (CISS) is a phenomenon in which electron
spins are polarized as they are transported through chiral molecules, and the
spin polarization depends on the handedness of the chiral molecule. In this
study, we show that spin selectivity can be realized in achiral materials by
coupling electrons to a single mode of a chiral optical cavity. By
investigating spin-dependent electron transport using the nonequilibrium
Green's function approach, the spin polarization in a two-terminal setup is
demonstrated to approach unity if the rate of dephasing is sufficiently small
and the average chemical potential of the two leads is within an appropriate
range of values, which is narrow because of the high frequency of the cavity
mode. To obtain a wider range of energies for a large spin polarization, we
propose to combine the CISS in chiral molecules with the light-matter
interactions. For demonstration, the spin polarization of electrons transported
through a helical molecule strongly coupled to a chiral cavity mode is
evaluated.
