Engineering the molecular structure to optimize the spin Hall signal in organics

TL;DR

This paper demonstrates how molecular engineering in organic materials can significantly enhance the spin Hall effect, bringing organic spintronics closer to inorganic systems by identifying key molecular features and potential high-performance candidates.

Contribution

It introduces a method to optimize spin Hall signals in organics through molecular design, focusing on heavy element substitution and torsion angles for enhanced spin-orbit coupling.

Findings

Spin Hall conductivity improved by over five orders of magnitude.

Spin Hall angle increased by more than three orders of magnitude.

Identification of organic molecules with exceptionally large spin Hall signals.

Abstract

In this study, by engineering the molecular structure, we optimize the spin Hall conductivity and the spin Hall angle in organics by more than five and three orders of magnitude, respectively. We identify two important characteristics of organic molecules, namely substitution of heavy elements and the torsion angles between constituent units of the polymer, which have significant effects on the spin Hall signal. These characteristics are directly related to the spin-orbit coupling and the energetic disorder, both of which offer a wide scope of chemical tunability in high-mobility polymers. We compute the spin Hall characteristics for easily synthesized molecules and identify candidates to exhibit the largest spin Hall signals in organic systems, several orders of magnitude larger than previously observed. The present study brings organic spintronics, by introducing polymers with much stronger spin Hall signal, closer to their inorganic counterparts.