Thermodynamic Observation of a Vortex Melting Transition in the Fe-based Superconductor Ba0.5K0.5Fe2As2

TL;DR

This study provides thermodynamic evidence of a vortex melting transition in Ba0.5K0.5Fe2As2, revealing significant thermal fluctuation effects on its superconducting phase diagram, similar to cuprates.

Contribution

First thermodynamic observation of vortex melting transition in an Fe-based superconductor using multiple experimental probes.

Findings

Thermodynamic signatures of vortex melting transition identified

Thermal fluctuations significantly influence superconducting properties

Vortex phase diagram characterized in Ba0.5K0.5Fe2As2

Abstract

In cuprate high-temperature superconductors the small coherence lengths and high transition termperatures result in strong thermal fluctuations, which render the superconducting transition in applied magnetic fields into a wide continuous crossover. A state with zero resistance is found only below the vortex melting transition, which occurs well below the onset of superconducting correlations. Here we investigate the vortex phase diagram of the novel Fe-based superconductor in form of a high-quality single crystal of Ba0.5K0.5Fe2As2, using three different experimental probes (specific heat, thermal expansion and magnetization). We find clear thermodynamic signatures of a vortex melting transition, which shows that the thermal fluctuations in applied magnetic fields also have a considerable impact on the superconducting properties of iron-based superconductors.