Experimental study of the incoherent spectral weight in the photoemission spectra of the misfit cobaltate [Bi2Ba2O4][CoO2]2

TL;DR

This study uses ARPES to distinguish coherent and incoherent spectral weights in misfit cobaltates, revealing a very small quasiparticle weight and providing a new method to quantify electronic correlations.

Contribution

It introduces a method to extract and compare coherent and incoherent spectral weights in ARPES data to estimate quasiparticle weight Z in cobaltates.

Findings

Quasiparticle weight Z is approximately 0.15.

The method reliably quantifies correlation strength.

Incoherent spectral weight analysis aids understanding of electron correlations.

Abstract

Previous ARPES experiments in NaxCoO2 reported both a strongly renormalized bandwidth near the Fermi level and moderately renormalized Fermi velocities, leaving it unclear whether the correlations are weak or strong and how they could be quantified. We explain why this situation occurs and solve the problem by extracting clearly the coherent and incoherent parts of the band crossing the Fermi level. We show that one can use their relative weight to estimate self-consistently the quasiparticle weight Z, which turns out to be very small Z=0.15 +/- 0.05. We suggest this method could be a reliable way to study the evolution of correlations in cobaltates and for comparison with other strongly correlated systems.