Breakdown of coherence in Kondo alloys: crucial role of concentration vs band filling

TL;DR

This paper investigates the breakdown of coherence in Kondo alloys by analyzing how impurity concentration and band filling affect low energy states, revealing potential violations of Luttinger's theorem and implications for experimental observations.

Contribution

It extends previous models by studying finite Kondo coupling on a Bethe lattice and incorporates finite-dimensional fluctuations via statistical-DMFT, revealing new physical insights.

Findings

Potential breakdown of Luttinger 'theorem' at certain impurity concentrations.

Local potential scattering can lie outside the conduction band.

Distributions of local potential scattering evolve with model parameters.

Abstract

We study the low energy states of the Kondo alloy model (KAM) as function of the magnetic impurity concentration per site, x, and the conduction electron average site occupation, nc. In previous works, two different Fermi liquid regimes had been identified at strong Kondo coupling JK, that may be separated by a transition at x=nc. Here, we analyze the KAM for finite JK on a Bethe lattice structure. First, using the mean-field coherent potential approximation (DMFT-CPA) which is exact at lattice coordination Z=infty, we show that the real part of the local potential scattering may be located outside the conduction electron band, revealing a possible breakdown of Luttinger 'theorem' for intermediate values of impurity concentration x. Unusual physical signatures are expected, e.g., in ARPES experiments. In order to take into account fluctuations associated with finite dimensionality,i.e., finite Z, we extend this analyze by also studying the KAM with an adaptation of the statistical-DMFT method that was developped elsewhere. We review the distributions of local potential scattering and their evolution with model parameters: concentration, strength of Kondo coupling, coordination number, local site neighborhood, connection with percolation issue. Relevence for Kondo alloys material with f-electrons is also discussed.