Effect of pressure on the structural phase transition and superconductivity in (B$_{1-x}K_x)Fe_2As_2 (x = 0 and 0.45) and SrFe_2As_2 single crystals

TL;DR

This study investigates how pressure affects the structural phase transition and superconductivity in various iron arsenide compounds, revealing linear decreases in transition temperatures and similar phase diagrams across different materials.

Contribution

It provides new insights into pressure-induced changes in phase transitions and superconductivity in iron arsenide single crystals, with detailed phase diagrams for multiple compounds.

Findings

Transition temperatures decrease linearly with pressure.

Upper critical field shifts downward under pressure.

Similar phase diagrams for different AFe2As2 compounds.

Abstract

The effects of pressure up to $\sim 20$ kbar, on the structural phase transition of SrFe$_2$As$_2$ and lightly Sn-doped BaFe$_2$As$_2$, as well as on the superconducting transition temperature and upper critical field of (Ba$_{0.55}$K$_{0.45}$)Fe$_2$As$_2$ single crystals have been studied. All the transition temperatures decrease with pressure in an almost linear fashion. Under pressure, the upper critical field curve, $H_{c2}(T)$, for (Ba$_{0.55}$K$_{0.45}$)Fe$_2$As$_2$ shifts down in temperature to follow the zero field $T_c$ with very little change in slope. Composite $P - T$ phase diagrams for three parent compounds, AFe$_2$As$_2$ (A = Ba, Sr, Ca), are constructed and appear to be remarkably similar: (i) having a structural (antiferromagnetic) phase transition line with a negative slope and (ii) showing signs of the emerging superconducting state at intermediate pressures.