Anomalous specific heat jump in the heavy fermion superconductor CeCoIn$_5$

TL;DR

This paper investigates the large specific heat jump in CeCoIn$_5$ superconductor, deriving an analytic expression within a coupled electron-boson framework and confirming it with experimental data, revealing insights into strong coupling effects.

Contribution

It introduces an analytic derivation of the specific heat jump in strong coupling superconductors using a coupled electron-boson model, validated by experimental data on CeCoIn$_5$.

Findings

Good agreement between theory and experiment for CeCoIn$_5$

Specific heat coefficient can be interpreted as a renormalization of degrees of freedom

Systematic change of specific heat jump with pressure observed

Abstract

We study the anomalously large specific heat jump and its systematic change with pressure in CeCoIn$_5$ superconductor. Starting with the general free energy functional of the superconductor for a coupled electron boson system, we derived the analytic result of the specific heat jump of the strong coupling superconductivity occurring in the coupled electron boson system. Then using the two component spin-fermion model we calculate the specific heat coefficient $C(T)/T$ both for the normal and superconducting states and show a good agreement with the experiment of CeCoIn$_5$. Our result also clearly demonstrated that the specific heat coefficient $C(T)/T$ of a coupled electron boson system can be freely interpreted as a renormalization either of the electronic or of the bosonic degrees of freedom.