Direct response of the spin-density wave transition and superconductivity to anion height inSrFe2As2

Abstract

We explored the effects of isovalent doping on the evolution of structure, spin-density wave (SDW), and superconductivity (SC) in three series of Ba-doped $\mathrm{SrF}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2\ensuremath{-}y}{\mathrm{P}}_{y}$ ($y=0.5,\phantom{\rule{0.16em}{0ex}}0.7,\phantom{\rule{0.16em}{0ex}}1.0$). For the $y=0.5$ series, the SDW and SC can coexist in the all-Ba-doped $\mathrm{SrF}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{1.5}{\mathrm{P}}_{0.5}$, while the SC first decreases and then saturates in the case of $y=0.7$. Besides, it is strikingly found that the SC of Ba-doped ${\mathrm{SrFe}}_{2}\mathrm{AsP}$ exhibits a dome-shaped ${T}_{\mathrm{c}}$, in which the anion height, ${h}_{\mathrm{pn}}$, approaching the optimal value of 1.308(2) \AA{} and the ${T}_{\mathrm{c}}$ simultaneously increase to the maxima. The phase diagrams of SDW and SC as a function of ${h}_{\mathrm{pn}}$ and Pn-Fe-Pn angle are first constructed here. It is argued that the isovalent substitutions in FeAs-based superconductors could significantly alter SC and ground states equally as well as carrier doping. The theoretical calculations show that electronic band structure is strongly dependent on the parameter of ${h}_{\mathrm{pn}}$ without introducing carriers by doping. The transition from three-dimensional-like to two-dimensional electronic states and the nesting of the Fermi surface can be realized by changing the ${h}_{\mathrm{pn}}$.