Structural distortion in Ludwigites

TL;DR

This paper investigates how static impurities affect structural distortions in Ludwigites, revealing that impurities suppress certain distortions and may explain differences between Fe and Co Ludwigites.

Contribution

It introduces a model with impurities and a tight-binding Hamiltonian to explain the suppression of structural distortions in Ludwigites.

Findings

Impurities block electron itinerancy and reduce structural order.

Reduction in distortion correlates with impurity number as 3^{-M}.

Explains absence of distortion in Co-Ludwigite.

Abstract

Structural distortion in a three-leg-ladder is studied in connection with Ludwigites, in particular the Fe and Co homometallic ones. Static impurities in t_{2g}-orbitals as infinite repulsion potentials randomly located in the three-leg-ladder and a Su-Schrieffer-Heeger like tight-binding Hamiltonian are proposed and discussed. It is found that such potentials block itinerant electrons and diminish a structural staggered order parameter, related with structural distortion, as 3^{-M} being M the number of impurities. This diminution is in detriment of Peierls like distortion that occurs in these ladders as in the case of Fe-Ludwigite. On the other hand, this diminution could explain the lack of structural distortion as in the case of Co-Ludwigite.