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.
Cite
@article{arxiv.cond-mat/0511554,
title = {Stripe correlations in Na$_{0.75}$CoO$_2$},
author = {J. Geck and M. v. Zimmermann and H. Berger and S. V. Borisenko and H. Eschrig and K. Koepernik and M. Knupfer and B. Büchner},
journal= {arXiv preprint arXiv:cond-mat/0511554},
year = {2007}
}