Stripe correlations in Na$_{0.75}$CoO$_2$

TL;DR

This study reveals sodium-density stripe formation in Na0.75CoO2 at low temperatures, linking sodium ordering to charge correlations in CoO2 layers, with implications for understanding similar phenomena in cuprates.

Contribution

It provides unambiguous experimental evidence and theoretical analysis demonstrating sodium-density stripes and their impact on electronic structure in Na0.75CoO2.

Findings

Sodium-density stripes are confirmed at low temperatures.

Stripe formation affects the Co electronic states near the Fermi level.

Na ordering is connected to charge correlations similar to cuprates.

Abstract

We unambiguously demonstrate, based on high-energy x-ray diffraction data and LDA calculations, that sodium-density stripes are formed in Na0.75CoO2 at low temperatures and rule out the previously proposed Na-ordering models. The LDA calculations prove, that the sodium-density stripes lead to a sizeable dip in the density of the Co-states at the Fermi level, pointing to band structure effects as a driving force for the stripe formation. This indicates that the sodium ordering is connected to stripe-like charge correlations within the CoO2 layers, leading to an astonishing similarity between the doped cuprates and the NaxCoO2 compounds.