Magnetic and superconducting transitions in Ba$_{1-x}$K$_x$Fe$_{2}$As$_{2}$ studied by specific heat

TL;DR

This study investigates the magnetic and superconducting phase transitions in Ba$_{1-x}$K$_x$Fe$_{2}$As$_{2}$ using specific heat measurements, revealing coexistence of magnetic order and superconductivity and characterizing the superconducting gap near optimal doping.

Contribution

First detailed specific heat analysis of Ba$_{1-x}$K$_x$Fe$_{2}$As$_{2}$ across different doping levels, identifying magnetic and superconducting transitions and their interplay.

Findings

Underdoped sample ($x=0.2$) shows both SDW and superconducting transitions.

Superconducting state near optimal doping fits a single-gap BCS model.

Electronic specific heat behavior varies with doping level.

Abstract

We report on specific heat measurements in Ba$_{1-x}$K$_x$Fe$_{2}$As$_{2}$ ($x\le 0.6$). For the underdoped sample with $x=0.2$ both the spin-density-wave transition at $T = 100$ K and the superconducting transition at 23 K can be identified. The electronic contribution to the specific heat in the superconducting state for concentrations in the vicinity of optimal doping $x=0.4$ can be well described by a full single-gap within the BCS limit.