Fluctuation contribution to the specific heat in non-Fermi models for superconductivity

TL;DR

This paper explores how non-Fermi liquid behavior affects the specific heat in two-dimensional superconductors, revealing a crossover from BCS to Bose-Einstein condensation by tuning a non-Fermi parameter, and matches theoretical predictions with experimental data.

Contribution

It introduces a model for fluctuation contributions to specific heat in non-Fermi superconductors and demonstrates a crossover between different superconducting regimes by varying a non-Fermi parameter.

Findings

Derived a fluctuation correction term involving temperature and the non-Fermi parameter.

Defined a coherence length that varies with the non-Fermi parameter, enabling crossover analysis.

Estimated the non-Fermi parameter for HTSC materials and calculated the critical temperature.

Abstract

We investigate the fluctuation contribution to the specific heat of a two-dimensional superconductor with a non-Fermi normal state described by a Anderson Green's function $G(k,i\omega)=\omega_c^{-\alpha}/(i\omega-\epsilon_k)^{1-\alpha}$. The specific heat corrections contain a term proportional to $(T^{2\alpha-T_c^{2\alpha}})^{-1}$ and another logarithmic one. We defined a coherence length as function of the non-Fermi parameter $\alpha$, which showed that a crossover study between BCS and Bose-Einstein condensation is possible by varying $\alpha$ in an interval $0 \div \alpha_{cr}$. By comparing our theoretical results with the experimental data for HTSC materials, we reobtained the value for $\alpha$, corresponding to such systems, of the order $0.3 \div 0.45$. We also reobtained the critical temperature for such a superconductor using the Thouless criterion.