An analytically tractable model of bad metals

TL;DR

This paper introduces an analytically solvable Kondo-type model that captures the two-stage screening process in bad metals, explaining non-Fermi liquid behavior in iron chalcogenides and ruthenates.

Contribution

It presents a simplified, analytically tractable model for bad metals that describes the two-stage orbital screening process and provides explicit analytical results for thermodynamic properties.

Findings

Two distinct energy scales for orbital screening and quasiparticle coherence.

Analytical expressions for specific heat and magnetic susceptibility at low temperatures.

Model explains non-Fermi liquid behavior observed in certain correlated materials.

Abstract

We discuss a model Kondo-type Hamiltonian representing an analytically tractable version of the model used by Yin {\it et.al.}, Phys. Rev. B{\bf 86}, 2399 (2012) to explain the non-Fermi liquid behavior of iron chalcogenides and ruthenates in an intermediate energy range. We consider a regime where a complete screening of the local degrees of freedom proceeds in two stages described by two characteristic energy scales $T_K^{orb} >> E_0$. The first scale marks a screening of the orbital degrees of freedom and the second one marks a crossover to the regime with coherent propagation of quasiparticles. We present analytical results for the specific heat and magnetic susceptibility at $T << T_K^{orb}$.