Superconductivity up to 30 K in the vicinity of quantum critical point in BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$

TL;DR

This study demonstrates that phosphorus doping in BaFe₂(As₁₋ₓPₓ)₂ induces bulk superconductivity up to 30 K near a magnetic quantum critical point, highlighting the link between quantum criticality and superconductivity in iron-based arsenides.

Contribution

It provides experimental evidence of superconductivity near a quantum critical point in BaFe₂(As₁₋ₓPₓ)₂, revealing the role of isovalent doping and magnetic quantum criticality.

Findings

Superconductivity with T_c up to 30 K observed at x=0.32.

Superconductivity disappears for x ≥ 0.77.

Linear resistivity indicates proximity to a quantum critical point.

Abstract

We report bulk superconductivity induced by an isovalent doping of phosphorus in BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$. The P-for-As substitution results in shrinkage of lattice, especially for the FeAs block layers. The resistivity anomaly associated with the spin-density-wave (SDW) transition in the undoped compound is gradually suppressed by the P doping. Superconductivity with the maximum $T_c$ of 30 K emerges at $x$=0.32, coinciding with a magnetic quantum critical point (QCP) which is evidenced by the disappearance of SDW order and the linear temperature-dependent resistivity in the normal state. The $T_c$ values were found to decrease with further P doping, and no superconductivity was observed down to 2 K for $x\geq$ 0.77. The appearance of superconductivity in the vicinity of QCP hints to the superconductivity mechanism in iron-based arsenides.