Pressure effects on the superconducting thin film Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$

TL;DR

This study investigates how applying pressure affects the superconducting transition temperature of a Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ thin film, revealing a dome-shaped Tc variation and insights into fluctuation-driven high-temperature superconductivity.

Contribution

It provides new experimental data on pressure dependence of Tc in a specific iron-based superconductor thin film, highlighting the role of lattice mismatch and normal state fluctuations.

Findings

Superconducting Tc peaks at 40.8 K under 11.8 kbar pressure.

Tc exhibits a dome-shaped dependence on pressure.

Normal state fluctuations are linked to high-temperature superconductivity.

Abstract

We report electrical resistivity measurements on a high-quality Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ thin film ($x=0.4$) under pressure. The superconducting transition temperature (=39.95 K) of the optimally-doped thin film shows a dome shape with pressure, reaching a maximal value 40.8 K at 11.8 kbar. The unusually high superconducting transition temperature and its anomalous pressure dependence are ascribed to a lattice mismatch between the LaAlO$_3$ substrate and the thin film. The local temperature exponent of the resistivity ($n=d\text{ln}\Delta\rho/d\text{ln}T$) shows a funnel shape around the optimal pressure, suggesting that fluctuations associated with the anomalous normal state are responsible for high-temperature superconductivity.