Spin-selective Transport in Semiconductor-based Chiral Molecular Junctions

Chirality-induced spin selectivity (CISS) is an effect with far-reaching fundamental implications involving intricate interplays among structural chirality, topological states, and electronic spin and orbitals. However, the microscopic picture of how chiral geometry influences electronic spin remains elusive. In this work, using a proven platform of chiral molecular spin valves of (Ga,Mn)As/AHPA-L/NM,¹ we directly compared the CISS magnetoconductance of devices with normal metal electrodes of contrasting spin-orbit coupling (SOC) strengths: A heavy-metal (Au) electrode was found to produce significantly greater magnetoconductance than light metals.² Our results evidence the essential role of SOC in the metal electrode for engendering the CISS spin valve effect, given the negligible SOC in organic molecules, which lends support to the scenario that the NM provides SOC to convert the orbital polarization induced by the chiral molecular structure to spin polarization.³ A tunneling model with a magnetochiral modulation of the potential barrier is shown to quantitatively account for the observation. Furthermore, we demonstrated that the CISS effect can be probed via the Hanle measurement in fully non-magnetic setup using a conventional semiconductor (GaAs).