Orbitally-driven Peierls state in spinels

TL;DR

This paper proposes that in certain spinels near an insulator-metal transition, an orbitally-driven Peierls state can form, explaining unusual superstructures like octamers and chiral arrangements observed experimentally.

Contribution

It introduces the concept of an orbitally-driven Peierls state in spinels with partially filled t2g levels, linking it to observed superstructures and predicting its occurrence in other systems.

Findings

Explains superstructures in CuIr2S4 and MgTi2O4 via orbitally-driven Peierls mechanism.

Suggests similar phenomena may occur in NaTiO2 and related materials.

Provides a theoretical framework connecting electronic structure to superstructure formation.

Abstract

We consider the superstructures, which can be formed in spinels containing on B-sites the transition-metal ions with partially filled t2g levels. We show that, when such systems are close to itinerant state (e.g. have an insulator-metal transition), there may appear in them an orbitally-driven Peierls state. We explain by this mechanism the very unusual superstructures observed in CuIr2S4 (octamers) and MgTi2O4 (chiral superstructures) and suggest that similar phenomenon should be observed in NaTiO2 and possibly in some other systems.