Polarization-dependent soft X-ray absorption of over-doped superconducting Sr2CuO3 + δ single crystal

In order to study the factors affecting superconductivity of Sr2CuO3 + δ, polarized X-ray absorption spectra (XAS) were measured at Cu L23 edge and O K edge of an over-doped single crystal specimen. This polarized XAS study reveals a distinctive anisotropic local electronic structure of Cu coordination: the unoccupied states are dominated by the in-plane components of Cu 3dx2 − y2 and O 2px,y. However, the signal from the unoccupied out-of-plane O 2pz and Cu 3dz2 states also appear. Furthermore, the detailed analysis of Cu L3-edge XAS at 300 K and 17.3 K indicates that the conductive carrier partly shifts from out-of-plane to in-plane in the superconducting state. Theoretical calculation of Cu L23-edge core level spectra based on Charge Transfer Multiplet theory is fairly consistent with above experimental results.