Resonant spin current in nanotube double junctions

TL;DR

This paper theoretically investigates how nanotube double junctions can generate and control spin-polarized currents through quantum well resonances and Coulomb interactions, acting as nanoscale spin filters.

Contribution

It introduces a theoretical model demonstrating spin current generation and control in nanotube double junctions using Coulomb interactions and gate voltages.

Findings

Spin current arises from Coulomb-induced spin degeneracy lifting.

Gate voltage can control the spin polarization direction.

Proper nanotube lengths enable effective spin filtering.

Abstract

Zero bias conductance per spin of nanotube double junction (NTDJ) is investigated theoretically using the tight binding model, unrestricted Hartree-Fock approximation and non-equilibrium Green's functions. NTDJ consists of two metallic nanotubes joined by a piece of semiconducting nanotube, with the transition between the nanotubes made up of sets of 5 and 7 member carbon rings. A quantum well forms in the central semiconducting NT region, bounded by Schottky barriers. Spin current occurs when Coulomb interactions raise the spin degeneracy of resonant levels in the quantum well. As long as an appropriate semiconducting NT length is chosen, spin direction can be controlled by gate voltage, i.e., NTDJ functions as a nano spin filter.