Transport properties of Co in Cu(100) from first principles

TL;DR

This study investigates the electronic transport properties of a Co atom on Cu(100) using first-principles calculations, revealing small spin-orbit coupling effects but significant influence of Coulomb interactions on spin-flip transmission, especially in contact regimes.

Contribution

First-principles analysis of Co/Cu(100) transport incorporating Coulomb interactions and spin-orbit coupling, highlighting their effects on spin-flip transmission and the Kondo effect.

Findings

Spin-flip transmission scales as λ^2/Γ^2 and is generally small.

Hubbard U can enhance spin-flip transmission by two orders of magnitude.

Transport in the tunneling regime is less affected by U and SOC.

Abstract

The electronic transport properties of a point-contact system formed by a single Co atom adsorbed on Cu (100) and contacted by a copper tip is evaluated in the presence of intra-atomic Coulomb interactions and spin-orbit coupling. The calculations are performed using equilibrium Green's functions evaluated within density functional theory completed with a Hubbard $U$ term and spin-orbit interaction, as implemented in the Gollum package. We show that the contribution to the transmission between electrodes of spin-flip components is negative and scaling as $\lambda^2/\Gamma^2$ where $\lambda$ is the SOC and $\Gamma$ the Co atom-electrode coupling. Hence, due to this unfavorable ratio, SOC effects in transport in this system are small. However, we show that the spin-flip transmission component can increase by two orders of magnitude depending on the value of the Hubbard $U$ term. These effects are particularly important in the contact regime because of the prevalence of $d$-electron transport, while in the tunneling regime, transport is controlled by the $sp$-electron transmission and results are less dependent on the values of $U$ and SOC. Using our electronic structure and the elastic transmission calculations, we discuss the effect of $U$ and SOC on the well-known Kondo effect of this system.