  Chiral molecules can selectively transport electrons of a particular spin
orientation, yet the underlying mechanism remain poorly understood. Here, we
present theoretical evidence that electrons propagating through chiral
materials with screw symmetry exhibit chirality themselves and carry
symmetry-induced pseudo-angular momentum (PAM) which must be characterized by
both spin and orbital components. The chiral electron transport is PAM
polarized, with counterpropagating states exhibiting opposite PAM. At
chiral-achiral interfaces, the PAM polarization is converted to spin
polarization due to wave function matching, thereby establishing a novel
principle for the chiral-induced spin selectivity.
