# Circuit-Model Analysis for Spintronic Devices with Chiral Molecules as Spin Injectors

## TL;DR

This paper introduces a circuit-model framework to quantitatively analyze the CISS effect in spintronic devices using chiral molecules, revealing limitations of current experimental signals and proposing enhancements with graphene.

## Contribution

The paper develops a circuit-model approach for quantitative evaluation of the CISS effect, providing insights into experimental signals and potential improvements with material modifications.

## Key findings

- Experimentally observed signals are too high to be solely due to CISS.
- Replacing silver with graphene can amplify spin signals by four orders of magnitude.
- The framework enables systematic analysis of spintronic experiments involving chiral molecules.

## Abstract

Recent research discovered that charge transfer processes in chiral molecules can be spin selective and named the effect chiral-induced spin selectivity (CISS). Follow-up work studied hybrid spintronic devices with conventional electronic materials and chiral (bio)molecules. However, a theoretical foundation for the CISS effect is still in development and the spintronic signals were not evaluated quantitatively. We present a circuit-model approach that can provide quantitative evaluations. Our analysis assumes the scheme of a recent experiment that used photosystem~I (PSI) as spin injectors, for which we find that the experimentally observed signals are, under any reasonable assumptions on relevant PSI time scales, too high to be fully due to the CISS effect. We also show that the CISS effect can in principle be detected using the same type of solid-state device, and by replacing silver with graphene, the signals due to spin generation can be enlarged four orders of magnitude. Our approach thus provides a generic framework for analyzing this type of experiments and advancing the understanding of the CISS effect.