Strong coupling resistivity in the Kondo model

TL;DR

This paper uses integrable quantum field theory to systematically analyze the strong coupling behavior of the Kondo model, deriving detailed resistivity expansions at low temperatures and comparing with numerical data.

Contribution

It develops a method to determine all irrelevant operators and their couplings exactly, extending the Fermi liquid resistivity expansion to arbitrary order in the Kondo model.

Findings

Resistivity expanded up to order T^6

Extended Nozieres T^2 result to higher orders

Good agreement with numerical data

Abstract

By applying methods of integrable quantum field theory to the Kondo problem, we develop a systematic perturbation expansion near the IR (strong coupling) fixed point. This requires the knowledge of an infinity of irrelevant operators and their couplings, which we all determine exactly. A low temperature expansion (ie all the corrections to Fermi liquid theory) of the resistivity then follows, extending for instance the well known Nozieres $T^2$ result in the exactly screened case to arbitrary order. The example of the ordinary Kondo model is worked out in details: we determine $\rho$ up to order $T^6$, and compare the result with available numerical data.