Dynamical CPA and Tight-Binding LMTO Approach to Correlated Electron System

TL;DR

This paper extends the dynamical CPA to realistic Hamiltonians combining tight-binding LMTO bands and Coulomb interactions, providing insights into electronic and magnetic properties of Fe and Ni at finite temperatures.

Contribution

It introduces a dynamical CPA framework with a functional integral approach for realistic Hamiltonians, enabling detailed analysis of correlated electron systems.

Findings

Band narrowing and 6 eV satellite observed in Ni at finite temperatures.

Calculated effective Bohr magneton numbers match experimental data.

Curie temperatures are overestimated but show qualitative agreement.

Abstract

Dynamical Coherent-Potential Approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding Linear Muffintin Orbital (LMTO) bands and intraatomic Coulomb interactions. Thermodynamic potential and self-consistent equations for Green function are obtained on the basis of the functional integral method and the harmonic approximation which neglects the mode-mode couplings between the dynamical potentials with different frequency. Numerical calculations have been performed for Fe and Ni within the 2nd-order dynamical corrections to the static approximation. The band narrowing of the quasiparticle states and the 6 eV satellite are obtained for Ni at finite temperatures. The theory leads to the Curie-Weiss law for both Fe and Ni. Calculated effective Bohr magneton numbers are 3.0 $\mu_{\rm B}$ for Fe and 1.2 $\mu_{\rm B}$ for Ni, explaining the experimental data. But calculated Curie temperatures are 2020 K for Fe and 1260 K for Ni, being still overestimated by a factor of two as compared with the experimental ones. Dynamical effects on electronic and magnetic properties are discussed by comparing with those in the static approximations.