Electronic structure of T∗-type $Nd_{1.4}Ce_{0.2S}r_{0.4}CuO_4$ studied by photoelectron spectroscopy

We present investigations of the electronic structure of T∗-type $Nd_{1.4}Ce_{0.2}Sr_{0.4}CuO_4$ by means of photoelectron spectroscopy. The CuO-hybridization for $Nd_{1.4}Ce_{0.2}Sr_{0.4}CuO_4$ seems to have a smaller value than in n-doped T'-HTSCs, but is slightly larger than e.g. for $Bi_2Sr_2CaCu_2O_{8−δ}$. We attribute this to the structural properties of these compounds. On the other hand, the effective Coulomb repulsion on the copper site for T∗ is found to be comparable to the electron doped systems. Concerning the mean NdO- hybridization within the rare-earth layers only small differences between $Nd_{1.4}Ce_{0.2}Sr_{0.4}CuO_4$ and T'-systems are observed. Doped Ce was confirmed to be tetravalent in both T'-and T∗-compounds. The CuO-valence band region shows no significant changes compared with other HTSCs