Orbital order induced metal-insulator transition in (La,Ca)MnO3

TL;DR

This paper investigates how orbital order influences the insulator-metal transition in (La,Ca)MnO3, showing that suppression of Jahn-Teller distortions and orbital ordering are key factors in this phase change.

Contribution

It provides experimental evidence linking orbital ordering and Jahn-Teller distortions to the metal-insulator transition in (La,Ca)MnO3, highlighting the coexistence of different electronic phases.

Findings

Suppression of Jahn-Teller distortions drives the transition.

Orbital ordered state characterized by large Q2 distortions.

Coexistence of orbital-ordered and disordered states near transition.

Abstract

We present evidence that the insulator to metal transition in (La,Ca)MnO3 near x~0.2 is driven by the suppression of coherent Jahn-Teller distortions, originating from d type orbital ordering. The orbital ordered state is characterised by large long-range Q2 distortions below To*-o'. Above To*-o' we find evidence for coexistence between an orbital-ordered and -disordered state. This behaviour is discussed in terms of electronic phases of an orbital ordered insulating and orbital-disordered metallic states.