Partial spin polarization of conductance in vertical bi-layer nanowire with rectangular and smooth lateral confinement potential

TL;DR

This study simulates electron transport in vertical bi-layer nanowires with different lateral confinement potentials, revealing how confinement shape influences spin polarization of conductance under magnetic fields.

Contribution

It introduces a detailed simulation of spin-dependent conductance in bi-layer nanowires considering different lateral confinement potentials and their effects on spin polarization.

Findings

Rectangular confinement leads to multiple energy minima and low spin polarization.

Smooth confinement results in higher potential for large spin polarization.

Achieving high spin polarization requires tuning magnetic field and Fermi energies.

Abstract

We simulate the electron transport in vertical bi-layer nanowire which can be fabricated in molecular beam epitaxy process with lateral confinement potential formed by means of cleaved overgrowth or surface oxidization methods giving rectangular and smooth side confinement, respectively. In calculations we take into account interaction between charge carriers using DFT within local spin density approximation. If magnetic field is perpendicular to the wire axis, pseudogaps are opened in energy dispersion relation E(k) what in conjunction with spin Zeeman shift of spin-up and spin-down subbands allows for quite high spin polarization of conductance. We find that in nanowire with rectangular lateral confinement potential, electron density has two maximums localized at wire edges in each layers. This modificates strongly all magnetosubbands giving up to four energy minimums in lowest subband and considerably diminishes widths of pseudogaps what translates into low maximal spin polarization of conductance, not exceeding $40\%$. This drawback is absent in wire with smooth lateral confinement. However, in order to gain a large spin polarization simultaneous tuning of magnetic field as well as the Fermi energies in both layers of nanowire are required.