Anomalous spectral weight in photoemission spectra of the hole doped Haldane chain Y2-xSrxBaNiO5

TL;DR

This study investigates the effects of hole doping on the electronic structure of the Haldane chain compound Y2-xSrxBaNiO5 using photoemission spectroscopy, revealing unusual spectral weight behavior linked to local structural changes.

Contribution

It provides new insights into the spectral weight redistribution in hole-doped Haldane chains, highlighting the role of local inhomogeneity and hybridization effects.

Findings

Spectral weight increases at the top of the valence band with doping.

No significant change near the Fermi energy upon doping.

Enhanced Ni 3d-O 2p hybridization due to local structural modifications.

Abstract

In this paper, we present photoemission experiments on the hole doped Haldane chain compound $Y_{2-x}Sr_xBaNiO_5$. By using the photon energy dependence of the photoemission cross section, we identified the symmetry of the first ionisation states (d type). Hole doping in this system leads to a significant increase in the spectral weight at the top of the valence band without any change in the vicinity of the Fermi energy. This behavior, not observed in other charge transfer oxides at low doping level, could result from the inhomogeneous character of the doped system and from a Ni 3d-O 2p hybridization enhancement due to the shortening of the relevant Ni-O distance in the localized hole-doped regions.