Superconductivity at 33 - 37 K in $ALn_2$Fe$_4$As$_4$O$_2$ ($A$ = K and Cs; $Ln$ = Lanthanides)

Si-Qi Wu; Zhi-Cheng Wang; Chao-Yang He; Zhang-Tu Tang; Yi Liu; Guang-Han Cao

doi:10.1103/PhysRevMaterials.1.044804

paper

Superconductivity at 33 - 37 K in $A L n_{2}$ Fe $_{4}$ As $_{4}$ O $_{2}$ ( $A$ = K and Cs; $L n$ = Lanthanides)

arXiv:1704.01488 · doi:10.1103/PhysRevMaterials.1.044804

Abstract

We have synthesized 10 new iron oxyarsenides, K $L n_{2}$ Fe $_{4}$ As $_{4}$ O $_{2}$ ( $L n$ = Gd, Tb, Dy, and Ho) and Cs $L n_{2}$ Fe $_{4}$ As $_{4}$ O $_{2}$ ( $L n$ = Nd, Sm, Gd, Tb, Dy, and Ho), with the aid of lattice-match [between $A$ Fe $_{2}$ As $_{2}$ ( $A$ = K and Cs) and $L n$ FeAsO] approach. The resultant compounds possess hole-doped conducting double FeAs layers, [ $A$ Fe $_{4}$ As $_{4}$ ] $^{2 -}$ , that are separated by the insulating [ $L n_{2}$ O $_{2}$ ] $^{2 +}$ slabs. Measurements of electrical resistivity and dc magnetic susceptibility demonstrate bulk superconductivity at $T_{c}$ = 33 - 37 K. We find that $T_{c}$ correlates with the axis ratio $c / a$ for all 12442-type superconductors discovered. Also, $T_{c}$ tends to increase with the lattice mismatch, implying a role of lattice instability for the enhancement of superconductivity.

8 pages, 6 figures, 2 tables

Superconductivity at 33 - 37 K in ALn2​Fe4​As4​O2​ (A = K and Cs; Ln = Lanthanides)

Abstract

Superconductivity at 33 - 37 K in $A L n_{2}$ Fe $_{4}$ As $_{4}$ O $_{2}$ ( $A$ = K and Cs; $L n$ = Lanthanides)