Contact effects in spin transport along double-helical molecules

TL;DR

This study investigates how contact configurations and asymmetries influence spin transport in double-helical molecules, revealing conditions under which spin polarization can be achieved without dephasing.

Contribution

It demonstrates that multiple terminals and electrode asymmetries enable spin-filtering effects in coherent spin transport along double-helical molecules.

Findings

No spin polarization in two-terminal devices with 1D electrodes.

Spin polarization appears with multiple terminals or finite-width electrodes.

Asymmetry enhances spin polarization magnitude.

Abstract

We report on spin transport along double-helical molecular systems by considering various contact configurations and asymmetries between the two helical strands in the regime of completely coherent charge transport. Our results reveal that no spin polarization appears in two-terminal molecular devices when coupled to one-dimensional electrodes. The same holds in the case of finite-width electrodes if there is a \emph{bottleneck} of one single site in the system electrode--molecule--electrode. Then, additional dephasing is necessary to induce spin-filtering effects. In contrast, nonzero spin polarization is found in molecular devices with multiple terminals or with two finite-width electrodes, each of them connected to more than one site of the molecule. Then, the magnitude of spin polarization can be enhanced by increasing the asymmetry between the two strands. We point out that the spin-filtering effects could emerge in double-helical molecular devices at low temperature without dephasing by a proper choice of the electrode number and the connection between the molecule and the electrodes.