Role of local structure distortion in the suppression of superconductivity for Eu3-xSrxBi2S4F4 system

Abstract As new family of superconductors with a layered structure, BiS 2 -based materials have attracted much interest. Eu 3 Bi 2 S 4 F 4 is a newly discovered member which shows superconductivity at 1.5 K without extrinsic doping, however, superconductivity is strongly suppressed by Sr-doping. In this contribution, we present, in terms of local atomic displacement, an insight into the relationship between Sr-doping and the suppression of superconductivity in Eu 3- x Sr x Bi 2 S 4 F 4 by Bi and Eu L 3 -edge X-ray absorption spectroscopy. Upon Sr-doping, the distance between Eu 3 F 4 blocking layers and BiS 2 layers is significantly elongated, accompanied by the breaking of Eu-S-Bi channel, which makes it more difficult to transfer electrons into BiS 2 layers. Moreover, distortions in the Bi-S1 plane increase with Sr content, reducing the overlap among Bi(6 p x /6 p y )-S(3 p ) orbitals within the superconducting plane. The decoupling between blocking and BiS 2 layers, as well as the distortions in the superconducting Bi-S1 plane, may contribute to the suppression of superconductivity in Sr-doped Eu 3 Bi 2 S 4 F 4 compounds.