Low energy properties of M-state tunneling systems in metals: New candidates for non-Fermi-liquid systems

TL;DR

This paper models the low energy behavior of M-state tunneling systems in metals, revealing their potential as non-Fermi-liquid candidates with observable Kondo temperatures, through a generalized renormalization group approach.

Contribution

It introduces a generalized multiplicative renormalization group transformation for M-level tunneling systems interacting with conduction electrons, connecting them to a known non-Fermi-liquid fixed point.

Findings

M-level systems scale towards an SU(M) x SU(Nf) fixed point.

Kondo temperature for realistic systems is in the 1-10 K range.

The model predicts non-Fermi-liquid behavior in certain tunneling systems.

Abstract

We construct a generalized multiplicative renormalization group transformation to study the low energy dynamics of a heavy particle tunneling among $M$ different positions and interacting with $N_f$ independent conduction electron channels. Using a $1/N_f$-expansion we show that this M-level scales towards a fixed point equivalent to the $N_f$ channel $SU(M) \times SU(N_f)$ Coqblin-Schrieffer model. Solving numerically the scaling equations we find that a realistic M-level system scales close to this fixed point (FP) and its Kondo temperature is in the experimentally observable range $1-10 K$.