Weakness of Correlation Effect Manifestation in BaNi2As2: ARPES and LDA+DMFT study
Abstract
The electronic spectral function of BaNi2As2 is investigated using both the angle-resolved photoemission spectroscopy (ARPES) and a combined computational scheme of local density approximation together with dynamical mean-field theory (LDA+DMFT). In contrast to well studied isostructural iron arsenide high temperature superconductors, the BaNi2As2 demonstrate weak correlation effects although Ni-3d elections have even lager on-site interaction than Fe-3d ones. LDA+DMFT effective mass enhancement for bands crossing the Fermi level is found to be only about 1.2 which agrees well with ARPES data. This reduction of the correlation manifestation with respect to iron pnictides comes from the increase of 3d-orbital filling, when going from Fe to Ni. The electron correlations cause remarkable reconstruction of the bare BaNi2As2 LDA band structure below -0.8 eV due to self-energy effect. A simplified toy model to understand weakness of correlation effects in BaNi2As2 and to describe the LDA+DMFT self-energy shape is discussed. For more realistic comparison of LDA+DMFT spectral function maps with ARPES data we take into account several experimental features: the photoemission cross-section, the experimental energy and angular resolutions and the photo-hole lifetime effects. Thus presented here LDA+DMFT calculations with experimental features included provide nearly qualitative agreement with ARPES data and assure the observation of a dramatic apparent decrease of the correlation strength compared to the Fe compounds.
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