Transition temperature model based on specific heat data of an FeAs-based superconductor

Abstract

In this article, we studied the specific heat data of iron-based superconductors LaO_{1− x} F _x FeAs (x = 0.1) and SmO_{1− x} F _x FeAs (x = 0.13, 0.12, and 0.1). (i) The contribution of phonons in specific heat above T_c depends exponentially on temperature. (ii) The specific heat has different contributions, and they change differently at T_c . This change must be the effect of a physical function on heat capacity. Therefore, transition temperature is defined by thermal parameters. For LaO_0.9F_0.1FeAs and SmO_0.87F_0.13FeAs, a transition point was evaluated at 22.11 and 26.32 K, respectively. This is in close agreement with the midpoint transition temperatures obtained from dc resistivity and magnetization experiments, where the modified electronic heat capacity led to the approximate value of the transition point in two samples. The jump, ΔC/γT _c, and the electronic and lattice heat capacity coefficients, γ and β, respectively, were evaluated.

Keywords:

• electronic specific heat
• oxypnictide superconductor
• phonon specific heat
• superconductivity