Spin filtering and entanglement detection due to spin-orbit interaction in carbon nanotube cross-junctions

TL;DR

This paper explores how spin-orbit interaction in carbon nanotube cross-junctions enables efficient spin filtering and provides new methods for detecting electron entanglement through noise correlations.

Contribution

It introduces a novel spin filter mechanism in nanotube junctions and links spin filtering to entanglement detection via noise analysis.

Findings

Effective spin filtering controlled by gate and magnetic field.

Full polarization achievable near Dirac points.

Distinct entanglement signatures in noise correlations.

Abstract

We demonstrate that due to their spin-orbit interaction carbon nanotube cross-junctions have attractive spin projective properties for transport. First, we show that the junction can be used as a versatile spin filter as a function of a backgate and a static external magnetic field. Switching between opposite spin filter directions can be achieved by small changes of the backgate potential, and a full polarization is generically obtained in an energy range close to the Dirac points. Second, we discuss how the spin filtering properties affect the noise correlators of entangled electron pairs, which allows us to obtain signatures of the type of entanglement that are different from the signatures in conventional semiconductor cross-junctions.