Electronic Phase Diagram of SrFe₂(As_(1-x)P_x)₂: Effect of Structural Dimensionality

We have investigated the electronic properties of SrFe$_2$(As$_{1-x}$P$_x$)$_2$ ($0\leqq x\leqq1$) single crystals with postannealing treatment and established a phase diagram of this system. The postannealing treatment reduced the residual resistivity in an antiferromagnetic-orthorhombic phase and enhanced the superconducting transition temperature to $T_{c, optimal}$=33\,K in the superconducting phase. The obtained phase diagram and electronic properties are similar to those of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ despite the large difference in lattice constants. This indicates that, for superconductivity, the dimensionality of the Fermi surface determined by the crystal structural anisotropy is less important than the pnictogen height from the Fe plane.