Evolution of electronic structure with dimensionality in divalent nickelates

We investigate the evolution of electronic structure with dimensionality (d ) of Ni-O-Ni connectivity in divalent nickelates, NiO (3-d), La2NiO4, Pr2Ni O4 (2-d), Y2BaNiO5 (1-d) and Lu2BaNi5 (0-d), by analyzing the valence band and the Ni 2p core-level photoemission spectra in conjunction with detailed many-body calculations including full multiplet interactions. Experimental results exhibit a reduction in the intensity of correlation-induced satell ite features with decreasing dimensionality. The calculations based on the cluster model, but evaluating both Ni 3d and O 2p related photoemission pro cesses on the same footing, provide a consistent description of both valenc e-band and core-level spectra in terms of various interaction strengths. Wh ile the correlation-induced satellite features in NiO is dominated by poorl y screened d(8) states as described in the existing literature, we find tha t the satellite features in the nickelates with lower dimensional Ni-O-Ni c onnectivity are in fact dominated by the over-screened d(10)L(2) states. It is found that the changing electronic structure with the dimensionality is primarily driven by two factors: (i) a suppression of the nonlocal contrib ution to screening; and (ii) a systematic decrease of the charge-transfer e nergy Delta driven by changes in the Madelung potential. [S0163-1829(99)096 19-8].