Chirality-induced Spin Selectivity in Molecular Spin Valves: Role of the Nonmagnetic Electrode*

Chirality-induced spin selectivity (CISS), an effect in which structural chirality engenders spin polarization in the electrical current from a nonmagnetic metal (NM) electrode, has been observed in a variety of chiral molecules with various experimental probes. However, the microscopic origin and device manifestations of CISS remain controversial. Most theoretical models consider chiral molecules as a spin filter, despite the generally small spin orbit coupling (SOC) in organic molecules. A recent theory posits that chiral molecules act as an orbital polarizer, and the SOC in nonmagnetic electrode converts the orbital polarization to spin polarization. Here, we report a comparison of CISS-induced magnetoconductance (MC) in vertical heterojunctions of (Ga,Mn)As/AHPA-L molecules/NM, between NM of Au and Al. The perpendicularly magnetized (Ga,Mn)As functions as a spin analyzer. The Au junctions show pronounced MC signals, which contain a large nonlinear-response component and a nontrivial-linear response component. In contrast, the MC of Al junctions are significantly diminished. Our observations suggest an important role for SOC in NM electrode in CISS-induced spin valve effect.