Specific Heat-Coefficient of YbAl3 Studied by Combined Nearly Free Electron Conduction Band Hybridized with Localized f Electrons with Correlation Effect

TL;DR

This study models the electronic specific heat of YbAl3 using a hybridized band approach incorporating correlation effects, successfully reproducing experimental temperature-dependent specific heat features.

Contribution

It introduces a combined band model with correlation effects for YbAl3, providing a quantitative match to experimental specific heat data.

Findings

Reproduces the two-peak structure of specific heat temperature dependence.

Highlights the role of correlation effects and density of states in specific heat behavior.

Demonstrates the model's applicability to heavy electron compounds with s- or p-electron conduction bands.

Abstract

Based on the recently proposed band model, the electronic specific heat of moderately heavy electron compound YbAl$_3$ are investigated. The band term of the Hamiltonian consists of three parts; conduction electrons described by the nearly free electron method, localized 4f electrons of Yb ions and the hybridization term between these electrons. Extracting several bands near the Fermi level, we reconstruct the low-energy effective Hamiltonian in order to consider the correlation effect, which is studied by using the self-consistent second order perturbation theory combined with local approximation. The temperature dependence of the specific heat $c_{\rm v}(T)$ is calculated as a function of temperature $T$ from the numerical derivative of the internal energy. Sommerfeld coefficient $\gamma$ is also calculated from the direct formula. The overall structure of $c_{\rm v}(T)/T$ is in quantitative agreement with the experimental results, which have the characteristic two-peak structures. They originate from the correlation effect and the structure of the non-interacting density of states, respectively. We show that our effective Hamiltonian yielding the realistic band structure may describe quantitatively heavy electron compounds with conduction bands composed of s- or p- electrons.