Orbital characters of three-dimensional Fermi surfaces in Eu2-xSrxNiO4   as probed by soft-x-ray angle-resolved photoemission spectroscopy
  The three-dimensional Fermi surface structure of hole-doped metallic layered nickelate Eu2-xSrxNiO4 (x=1.1), an important counterpart to the isostructural superconducting cuprate La2-xSrxCuO4, is investigated by energy-dependent soft-x-ray angle-resolved photoemission spectroscopy. In addition to a large cylindrical hole Fermi surface analogous to the cuprates, we observe a Gamma-centered 3z2-r2-derived small electron pocket. This finding demonstrates that in the layered nickelate the 3z2-r2 band resides close to the x2-y2 one in energy. The resultant multi-band feature with varying orbital character as revealed may strongly work against the emergence of the high-temperature superconductivity. 
M. Uchida, K. Ishizaka, P. Hansmann, X. Yang, M. Sakano, J. Miyawaki,   R. Arita, Y. Kaneko, Y. Takata, M. Oura, A. Toschi, ...
cond-mat.str-el cond-mat.mtrl-sci