Non-equilibrium spin accumulation and magneto-conductance in chiral nanojunctions from density-functional $\&$ group theory

TL;DR

This paper demonstrates through non-equilibrium DFT calculations that breaking certain symmetries in chiral nanojunctions induces spin accumulation and magneto-conductance, elucidating mechanisms behind chirality-induced spin selectivity.

Contribution

It provides a theoretical framework showing how symmetry breaking leads to spin accumulation and magneto-conductance in non-magnetic chiral systems under bias.

Findings

Net spin accumulation appears at finite bias when symmetries are broken.

Magneto-conductance arises with a magnetized detector due to spin accumulation.

Symmetry conditions for spin polarization are similar to those for spin accumulation.

Abstract

It is theoretically well established that a spin-dependent electron transmission generally appears in chiral systems, even without magnetic components, as long as a strong spin-orbit coupling is present in some of its elements. However, how this translates into the so-called chirality-induced spin selectivity in experiments, where the system is taken out of equilibrium, is still debated. Aided by non-equilibrium DFT-based quantum transport calculations, here we show that, when spatial symmetries that forbid a finite spin polarization in equilibrium are broken, a \textit{net} spin accumulation appears at finite bias in an arbitrary two-terminal nanojunction. Furthermore, when a suitably magnetized detector is introduced in the system, the net spin accumulation, in turn, translates into a finite magneto-conductance. The symmetry prerequisites are mostly analogous to those for the spin polarization at any bias, with the vectorial nature given by the direction of magnetization.