Electron Transfer and Local Atomic Displacement in Sr1–xCexFBiS2 Revealed by X-ray Absorption Spectroscopy

Abstract

Superconductivity in quasi-two-dimensional crystal structures has attracted sustained interest among condensed matter community, primarily due to their exotic superconducting properties. Recently, superconductivity of BiS2-based compounds with the desired layered crystal structure has been reported. In this contribution, Ce-doping effect on the electronic structure and local atomic displacement of Sr1–xCexFBiS2 was investigated by Ce and Bi L3-edge X-ray absorption spectroscopy. Upon Ce-doping both the Ce–S2 and Bi–S2 bonds shrink, enhancing the coupling between Sr/CeF and superconducting BiS2 layers. Therefore, Ce substitution provides electron carriers to the superconducting BiS2 layers through the enhanced Ce–S2–Bi channel. On the other hand, Ce-doping effectively modulates the in-plane structure of Bi–S1 plane. In Ce-doped compounds both the shortening of in-plane Bi–S1 bond and the flatter Bi–S1 plane would enhance overlap of Bi(6px/6py)–S(3p) orbitals within the superconducting plane. Therefore, Ce-...