Specific heat of a non-local attractive Hubbard model

TL;DR

This paper investigates the specific heat behavior of a non-local attractive Hubbard model, revealing a two-peak structure influenced by correlations, pseudogap effects, and second nearest neighbor hopping.

Contribution

It introduces a two-pole approximation to analyze the specific heat and correlation functions, highlighting the impact of pseudogaps and hopping on thermal properties.

Findings

Two-peak structure in specific heat for certain parameters

Pseudogap suppresses the high-temperature peak

Second nearest neighbor hopping modifies specific heat features

Abstract

The specific heat of an attractive (interaction $G<0$) non-local Hubbard model is investigated. We use a two-pole approximation which leads to a set of correlation functions. In particular, the correlation function $\ <\vec{S}_i\cdot\vec{S}_j\ >$ plays an important role as a source of anomalies in the normal state of the model. Our results show that for a giving range of $G$ and $\delta$ where $\delta=1-n_T$ ($n_T=n_{\uparrow}+n_{\downarrow}$), the specific heat as a function of the temperature presents a two peak structure. Nevertehelesss, the presence of a pseudogap on the anti-nodal points $(0,\pm\pi)$ and $(\pm\pi,0)$ eliminates the two peak structure, the low temperature peak remaining. The effects of the second nearest neighbor hopping on the specific heat are also investigated.