Linear and Nonlinear Two-Terminal Spin-Valve Effect from Chirality-Induced Spin Selectivity

Abstract

Various mechanisms of electrical generation of spin polarization in <i>nonmagnetic</i> materials have been a subject of broad interest for their underlying physics and device potential in spintronics. One such scheme is chirality-induced spin selectivity (CISS), with which structural chirality leads to different electric conductivities for electrons of opposite spins. The resulting effect of spin filtering has been reported for a number of chiral molecules assembled on different surfaces. However, the microscopic origin and transport mechanisms remain controversial. In particular, the fundamental Onsager relation was argued to preclude linear-response detection of CISS by a ferromagnet. Here, we report definitive observation of CISS-induced magnetoconductance in vertical heterojunctions of (Ga,Mn)As/AHPA-L molecules/Au, directly verifying spin filtering by the AHPA-L molecules <i>via</i> spin detection by the (Ga,Mn)As. The pronounced and robust magnetoconductance signals resulting from the use of a magnetic semiconductor enable a rigorous examination of its bias dependence, which shows both linear- and nonlinear-response components. The definitive identification of the linear-response CISS-induced two-terminal spin-valve effect places an important constraint for a viable theory of CISS and its device manifestations. The results present a promising route to spin injection and detection in semiconductors without using any magnetic material.