Weakness of Correlation Effect Manifestation in BaNi$_2$As$_2$: ARPES and LDA+DMFT study

TL;DR

This study combines ARPES experiments and LDA+DMFT calculations to show that BaNi$_2$As$_2$ exhibits weak electronic correlation effects, contrasting with iron-based superconductors, due to increased 3d-orbital filling and resulting in minimal mass enhancement.

Contribution

The paper demonstrates the weak correlation effects in BaNi$_2$As$_2$ through combined experimental and theoretical analysis, highlighting the impact of 3d-orbital filling on correlation strength.

Findings

LDA+DMFT effective mass enhancement is about 1.2, matching ARPES data.

Correlation effects cause significant band structure reconstruction below -0.8 eV.

Weak correlation effects are due to increased 3d-orbital filling from Fe to Ni.

Abstract

The electronic spectral function of BaNi$_2$As$_2$ 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 BaNi$_2$As$_2$ 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 BaNi$_2$As$_2$ LDA band structure below $-0.8$ eV due to self-energy effect. A simplified toy model to understand weakness of correlation effects in BaNi$_2$As$_2$ 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.