Incoherent chiral-induced spin selectivity

TL;DR

This paper investigates the mechanisms behind spin-dependent transport in organic chiral molecules, revealing that phonon-assisted hopping can produce strong spin polarization despite weak spin-orbit coupling, explaining large room-temperature effects.

Contribution

It demonstrates that localization and phonon-induced decoherence do not prevent significant spin selectivity, decoupling the effect from the strength of spin-orbit coupling in long molecules.

Findings

Strong spin polarization persists despite phonon-induced decoherence.

Hopping mechanisms decouple spin selectivity from spin-orbit coupling magnitude.

Large room-temperature spin selectivity can be explained by hopping processes.

Abstract

The observation of spin-dependent transport through organic chiral structures has sparked numerous fundamental and applicative questions ranging from biology to spintronics. By now, there is a broad consensus that the effect results from the combination of spin-orbit coupling and the systems' unique geometry. However, two key challenges remain. Firstly, accounting for the magnitude of the measured effect in light of the weak spin-orbit coupling in organic systems. Secondly, understanding its observation not only in tunneling-dominated short molecules, but also in longer ones where phonon-assisted hopping via localized states is operative. We focus on the latter and find that localization and the complete loss of coherence due to phonons do not impede strong spin polarization of charge carriers passing through the molecule. Moreover, hopping decouples the energy scale for observing spin-selective transport from the magnitude of the spin-orbit coupling. Thus, our result may explain the observation of large spin selectivity at room temperature and under large applied voltages.