Atomic carbon chains as spin-transmitters: an \textit{Ab initio} transport study

TL;DR

This study uses ab initio calculations to show that atomic carbon chains connecting graphene flakes can act as spin-transmitters with highly spin-polarized electron transport, controllable via chemical, mechanical, or electrical modifications.

Contribution

It demonstrates for the first time that atomic carbon chains can serve as spin-polarized transmitters in graphene-based systems, revealing a new mechanism for spin control in molecular electronics.

Findings

Complete spin-polarization of transmission in large energy ranges.

Spin-splitting caused by zig-zag edge terminations.

Transmission controlled by chemical, mechanical, or electrical modifications.

Abstract

An atomic carbon chain joining two graphene flakes was recently realized in a ground-breaking experiment by Jin {\it et al.}, Phys. Rev. Lett. {\bf 102}, 205501 (2009). We present {\it ab initio} results for the electron transport properties of such chains and demonstrate complete spin-polarization of the transmission in large energy ranges. The effect is due to the spin-polarized zig-zag edge terminating each graphene flake causing a spin-splitting of the graphene $\pi_z$ bands, and the chain states. Transmission occurs when the graphene $\pi$-states resonate with similar states in the strongly hybridized edges and chain. This effect should in general hold for any $\pi$-conjugated molecules bridging the zig-zag edges of graphene electrodes. The polarization of the transmission can be controlled by chemically or mechanically modifying the molecule, or by applying an electrical gate.