Electronic structure studies on the n-type doped superconductors R2−xMxCuO4−δ (R=Pr,Nd,Sm; M=Ce,Th) and Nd2CuO4−xFx by electron-energy-loss spectroscopy

Abstract

The electronic structure of the high-Tc superconductors R2−xMxCuO4−δ (R=Pr, Nd, Sm; M=Ce, Th) and Nd2CuO3.8F0.2 has been studied by high-energy electron-energy-loss spectroscopy in transmission. Core-level spectroscopy, particularly on O 1s and Cu 2p levels yields information on the partial unoccupied density of states near the Fermi level, while that on R and Ce 3d and 4d levels may serve as a valence monitor for these constituents. A pre-edge structure in the O 1s spectrum is polarized in the CuO2 plane and assigned to transitions into a two-dimensional conduction band consisting of Cu 3d hybridized to O 2p states. In the Cu 3d9 configuration we found a slight admixture (∼10%) of Cu 3d3z2-r2 to the Cu 3dx2-y2 hole states similar to the p-type doped superconductors. Upon doping we recognized a reduction (∼14%) of the excitonic Cu 2p3/2 line, indicating that the introduced electrons go onto the Cu sites, thus producing charge carriers having predominantly Cu 3d character.

Source-reported materials — not catalogue approval

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