Spin selectivity through chiral polyalanine monolayers on semiconductors

TL;DR

This paper provides direct experimental evidence of chirality-induced spin selectivity (CISS) in chiral molecule-based devices on magnetic semiconductors, demonstrating spin filtering and detection that challenge traditional reciprocity principles.

Contribution

It reports the first direct observation of CISS in two-terminal semiconductor devices, revealing a spin valve effect that operates without magnetic materials and defies Onsager reciprocity.

Findings

Observation of linear and nonlinear magnetoconductance signatures of CISS

Verification of spin filtering and detection in chiral molecule devices

Demonstration of spin valve effect without magnetic materials

Abstract

Electrical generation of polarized spins in nonmagnetic materials is of great interest for the underlying physics and device potential. One such mechanism 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. However, the microscopic mechanism and manifestation of CISS in practical device structures remain controversial; in particular, the Onsager relation is understood to preclude linear-response detection of CISS by a ferromagnet. Here, we report direct evidence of CISS in two-terminal devices of chiral molecules on the magnetic semiconductor (Ga,Mn)As: In vertical heterojunctions of (Ga,Mn)As/AHPA-L molecules/Au, we observed characteristic linear- and nonlinear-response magnetoconductance, which directly verifies spin filtering by the AHPA-L molecules and spin detection by the (Ga,Mn)As. The results constitute definitive signature of CISS-induced spin valve effect, a core spintronic functionality, in apparent violation of the Onsager reciprocity. The results present a promising route to semiconductor spintronics free of any magnetic material.