  Topological aspects of the geometry of DNA and similar chiral molecules have
received a lot of attention, while the topology of their electronic structure
is less explored. Previous experiments have revealed that DNA can efficiently
filter spin-polarized electrons between metal contacts, a process called
chiral-induced spin-selectivity (CISS). However, the underlying correlation
between chiral structure and electronic spin remains elusive. In this work, we
reveal an orbital texture in the band structure, a topological characteristic
induced by the chirality. We find that this orbital texture enables the chiral
molecule to polarize the quantum orbital. This orbital polarization effect
(OPE) induces spin polarization assisted by the spin-orbit interaction from a
metal contact and leads to magnetorestistance and chiral separation. The
orbital angular momentum of photoelectrons also plays an essential role in
related photoemission experiments. Beyond CISS, we predict that OPE can induce
spin-selective phenomena even in achiral but inversion-breaking materials.

Mesoscale and Nanoscale Physics;Materials Science