Heat capacity jump at Tc and pressure derivatives of superconducting transition temperature in the Ba1-xKxFe2As2 (0.2 < x < 1.0) series

TL;DR

This study investigates how pressure and potassium doping affect the heat capacity and transition temperature in Ba1-xKxFe2As2 superconductors, revealing anomalies near x ~ 0.7 indicative of a Lifshitz transition.

Contribution

It provides new insights into the pressure dependence and heat capacity behavior across different doping levels, highlighting a possible Lifshitz transition near x ~ 0.7.

Findings

Weak but distinct pressure derivative anomaly near x ~ 0.7

Deviation of ΔCp at Tc from T^3 scaling near x ~ 0.7

Evidence supporting a Lifshitz transition in the material

Abstract

We present the evolution of the initial (up to ~ 10 kbar) hydrostatic, pressure dependencies of Tc and of the ambient pressure jump in the heat capacity associated with the superconducting transition as a function of K - doping in the Ba1-xKxFe2As2 family of iron-based superconductors. The pressure derivatives show weak but distinct anomaly near x ~ 0.7. In the same concentration region Delta Cp at Tc deviates from the Delta Cp ~ T^3 scaling found for most BaFe2As2 - based superconductors. These results are consistent with a Lifshitz transition, and possible significant modification of the superconducting state, occurring near x ~ 0.7.