Kondo Conductance in an Atomic Nanocontact from First Principles

TL;DR

This paper presents a first-principles method combining DFT and NRG to accurately calculate Kondo conductance in atomic nanocontacts, revealing detailed magnetic and geometric influences on conductance anomalies.

Contribution

It introduces a novel approach linking DFT and NRG for first-principles conductance calculations in nanocontacts, enabling detailed analysis of Kondo effects.

Findings

Fano-like conductance lineshape controlled by impurity s-level

Conductance anomaly depends on contact geometry

Discovery of opposite antiferromagnetic and ferromagnetic Kondo screening

Abstract

The electrical conductance of atomic metal contacts represents a powerful tool to detect nanomagnetism. Conductance reflects magnetism through anomalies at zero bias -- generally with Fano lineshapes -- due to the Kondo screening of the magnetic impurity bridging the contact. A full atomic-level understanding of this nutshell many-body system is of the greatest importance, especially in view of our increasing need to control nanocurrents by means of magnetism. Disappointingly, zero bias conductance anomalies are not presently calculable from atomistic scratch. In this Letter we demonstrate a working route connecting approximately but quantitatively density functional theory (DFT) and numerical renormalization group (NRG) approaches and leading to a first-principles conductance calculation for a nanocontact, exemplified by a Ni impurity in a Au nanowire. A Fano-like conductance lineshape is obtained microscopically, and shown to be controlled by the impurity s-level position. We also find a relationship between conductance anomaly and geometry, and uncover the possibility of opposite antiferromagnetic and ferromagnetic Kondo screening -- the latter exhibiting a totally different and unexplored zero bias anomaly. The present matching method between DFT and NRG should permit the quantitative understanding and exploration of this larger variety of Kondo phenomena at more general magnetic nanocontacts.