Conductance of single-atom magnetic junctions: A first-principles study

TL;DR

This study uses first-principles calculations to analyze the conductance of single-atom magnetic junctions, revealing that the conductance often deviates from the half quantum value due to spin-dependent effects.

Contribution

It demonstrates that the contact conductance in single-atom magnetic junctions varies significantly and is influenced mainly by the minority $d$ orbitals, challenging previous assumptions.

Findings

Contact conductance varies from approximately $G_0/2$ to over $1.7G_0$.

Deviation from $G_0/2$ is mainly due to spin-down conductance changes.

Spin-up conductance remains relatively constant across different junctions.

Abstract

We present a first-principles investigation to show that the contact conductance of a half conductance quantum ($G_0/2$) found previously does not generally hold for single-atom magnetic junctions composed of a tip and an adatom dsorbed on a surface. The contact conductance of the Ni-Co/Co(111) junction is approximately $G_0/2$, while for the Co-Co/Co(111), Ni-Ni/Ni(111), and Ni-Ni/Ni(001) junctions the contact conductances are 0.80$G_0$, 1.55$G_0$, and 1.77$G_0$, respectively. The deviation from $G_0/2$ is mainly caused by the variation of the spin-down conductance largely determined by the minority $d$ orbitals, as the spin-up one changes little for different junctions.