Sr2VO3FeAs : a Fe-pnictide superconductor with an insulating oxide layer

Abstract

Sr2VO3FeAs is a new high-Tc superconductor consisting of a stacking of anti-fluorite FeAs layers and perovskite-type Sr2VO3 layers. One of the key issues for Sr2VO3FeAs is whether Sr2VO3FeAs superconductor can be classified within the same class of previously known Fe-based superconductors. Recent first-principle calculations suggest that the Fermi surface can vary significantly depending on the nature of the V-states in the Sr2VO3 layer. Thus the understanding the properties of the Sr2VO3 layer is essential for addressing this issue. We investigate (1) Fe-site substitution effects on polycrystalline Sr2VO3FeAs with Mn, Co and Ru and (2) anisotropy of the upper critical fields for Sr2VO3FeAs single crystals.We carried out Fe-site substitution with Co, Mn and Ru for Sr2VO3FeAs and studied their magnetic and transport properties. Upon Co doping, as an electron doping，the system becomes more metallic with reduction of Tc, similar to the behavior of over-doped Fe-pnictides. For Mn doping, &not

as hole doping, the resistivity shows an insulating behavior with a rapid suppression of the superconductivity. The superconductivity remains intact by isovalent Ru substitution. These results are quite similar to previous Fe-site doped Fe-pnictide superconductors. We found that the FeAs layer plays a dominant role on the charge conduction, thus the Sr2VO3 layers should be considered as an insulating block. The strong anisotropy in Hc2 for single crystal also confirms this conclusion. Therefore, the FS is determined by the Fe bands, thus, Sr2VO3FeAs belongs to the same class of the previously known FeBSC.