New electronic orderings observed in cobaltates under the influence of misfit periodicities

TL;DR

This paper investigates how misfit periodicities in layered cobaltates influence their electronic structure, revealing new electronic orderings through ARPES and STM studies, especially under incommensurate conditions.

Contribution

It demonstrates that misfit potentials induce a novel form of electronic ordering in cobaltates, observable even in incommensurate phases, expanding understanding of layered correlated materials.

Findings

Misfit potentials affect Fermi surface evolution.

Electronic localization occurs at low doping.

Ordered stripe patterns observed in STM images.

Abstract

We study with ARPES the electronic structure of CoO2 slabs, stacked with rock-salt (RS) layers exhibiting a different (misfit) periodicity. Fermi Surfaces (FS) in phases with different doping and/or periodicities reveal the influence of the RS potential on the electronic structure. We show that these RS potentials are well ordered, even in incommensurate phases, where STM images reveal broad stripes with width as large as 80\AA. The anomalous evolution of the FS area at low dopings is consistent with the localization of a fraction of the electrons. We propose that this is a new form of electronic ordering, induced by the potential of the stacked layers (RS or Na in NaxCoO2) when the FS becomes smaller than the Brillouin Zone of the stacked structure.