Non-Fermi liquid behavior in transport through Co doped Au chains

TL;DR

This paper investigates the non-Fermi liquid behavior in electron transport through Co-doped Au chains, revealing complex Kondo physics and quantum criticality using a combination of ab initio calculations and numerical renormalization group analysis.

Contribution

The study constructs an effective model based on ab initio data and analyzes non-Fermi liquid behavior in Co-doped Au chains with NRG, highlighting quantum critical phenomena.

Findings

Low-temperature conductance follows $G(T)=a-b \, \sqrt{T}$

Impurity entropy approaches $\ln(2)/2$ at low temperatures

Stretching the chain induces a transition to a non-Kondo phase

Abstract

We calculate the conductance as a function of temperature $G(T)$ through Au monoatomic chains containing one Co atom as a magnetic impurity, and connected to two conducting leads with a 4-fold symmetry axis. Using the information derived from {\it ab initio} calculations, we construct an effective model $\Heff$ that hybridizes a 3d$^7$ quadruplet at the Co site with two 3d$^8$ triplets through the hopping of 5d$_{xz}$ and 5d$_{yz}$ electrons of Au. The quadruplet is split by spin anisotropy due to spin-orbit coupling. Solving $\Heff$ with the numerical renormalization group (NRG) % Wb: reverted my own change we find that at low temperatures $G(T)=a-b \sqrt{T}$ and the ground state impurity entropy is $\ln(2)/2$, a behavior similar to the two-channel Kondo model. Stretching the chain leads to a non Kondo phase, with the physics of the underscreened Kondo model at the quantum critical point.