Superconductivity and Crystal Structures of (Ba1-xKx)Fe2As2 (x = 0 - 1)

TL;DR

This study explores how doping with potassium affects the crystal structure and superconducting properties of (Ba1-xKx)Fe2As2, revealing structural-electronic coupling and superconductivity across the entire doping range.

Contribution

It provides detailed insights into the doping-dependent structural parameters and their correlation with superconductivity in (Ba1-xKx)Fe2As2, highlighting the coexistence of superconductivity with structural distortion.

Findings

Superconductivity persists across the entire doping range.

Maximum Tc of 38 K at x ~ 0.4.

Structural changes are coupled to electronic states.

Abstract

We report on doping dependencies of structural parameters and superconducting transition temperatures in the solid solution (Ba1-xKx)Fe2As2. As the main effect of doping on the crystal structure, we find linear decreasing As-Fe-As bond angles and Fe-Fe distances, equivalent to an elongation of the FeAs4 tetrahedra along [001]. The structural changes are intimately coupled to the electronic states at the Fermi level, because the most relevant Fe-3dx2-y2 orbitals are strongly affected by the As-Fe-As bond angle. Superconductivity is present over the whole doping range in (Ba1-xKx)Fe2As2 with a maximum Tc of 38 K at x ~ 0.4. The superconducting transitions in the orthorhombic compounds (Ba0.9K0.1)Fe2As2 (Tc ~ 3 K) and (Ba0.8K0.2)Fe2As2 (Tc ~ 25 K) is strong evidence for the coexistence of superconductivity with the structurally distorted and potentially magnetically ordered state in the BaFe2As2 family of iron arsenide superconductors.