Non-fermi-liquid behavior in transport through co-doped Au Chains

Abstract

We calculate the conductance as a function of temperature G ( T ) through Au monatomic chains containing one Co atom as a magnetic impurity, and connected to two conducting leads with a fourfold symmetry axis. Using the information derived from ab initio calculations, we construct an effective model ˆ H eff that hybridizes a 3 d 7 quadruplet at the Co site with two 3 d 8 triplets through the hopping of 5 d x z and 5 d y z electrons of Au. The quadruplet is split by spin anisotropy due to spin-orbit coupling. Solving ˆ H eff with the numerical renormalization group we find that at low temperatures G ( T ) = a − b √ 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.