Specific heat jump at superconducting transition in the presence of Spin-Density-Wave in iron-pnictides

TL;DR

This paper investigates how the specific heat jump at the superconducting transition in iron-pnictides is affected by the coexistence with spin-density-wave order, revealing deviations from BCS theory and behavior near the tri-critical point.

Contribution

It provides a theoretical analysis of the specific heat jump in superconductors coexisting with magnetic order, highlighting its variation near the tri-critical point and deep in the magnetic phase.

Findings

/T_c peaks at the tri-critical point.

/T_c decreases with lower T_c, roughly as T_c^2.

/T_c drops exponentially at very low T_c.

Abstract

We analyze the magnitude of the specific heat jump \Delta C at the superconducting transition temperature T_c in the situation when superconductivity develops in the pre-existing antiferromagnetic phase. We show that \Delta C/T_c differs from the BCS value and is peaked at the tri-critical point where this coexistence phase first emerges. Deeper in the magnetic phase, the onset of coexistence, T_c, drops and \Delta C/T_c decreases, roughly as \Delta C/T_c \propto T^2_c at intermediate T_c and exponentially at the lowest T_c, in agreement with the observed behavior of \Delta C/T_c in iron-based superconductors.