Effects of Ce and F substitutions on the electronic structure of Nd2CuO4 superconductors.

Abstract

The changes incurred by the replacement of Nd (or O) by Ce (or F) atoms on the electronic energy states of the superconducting ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$ compounds have been investigated in a tight-binding approximation. A minimum number of parameters have been employed in the calculation. The various peaks observed in the direct and inverse photoemission data of Reihl et al. are well explained. The calculated shift in Fermi level with x (or y) in ${\mathrm{Nd}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ (or ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{F}}_{\mathit{y}}$) is seen to be in agreement with the experiment. Further, our model detects an unoccupied Cu 4s band just at the conduction-band edge, as has been detected in electron-spin-resonance experiments.