Domain Formation and Orbital Ordering Transition in a Doped Jahn-Teller Insulator

TL;DR

This paper investigates how doping affects the orbital order and electronic properties of a Jahn-Teller insulator, revealing a transition from an ordered insulating state to a disordered metallic phase.

Contribution

It introduces a real space Monte-Carlo approach to study inhomogeneous states in a doped Jahn-Teller insulator, highlighting the orbital order-disorder transition and associated metallic behavior.

Findings

Doping induces hole-rich disordered regions within the orbitally ordered insulator.

Orbital order to disorder transition coincides with the emergence of metallic conductivity.

Spatial patterns of lattice distortions and charge densities elucidate the low doping phase diagram.

Abstract

The ground state of a double-exchange model for orbitally degenerate $e_g$ electrons with Jahn-Teller lattice coupling and weak disorder is found to be spatially inhomogeneous near half filling. Using a real space Monte-Carlo method we show that doping the half-filled orbitally ordered insulator leads to the appearance of hole-rich disordered regions in an orbitally ordered environment. The doping driven orbital order to disorder transition is accompanied by the emergence of metallic behavior. We present results on transport and optical properties along with spatial patterns for lattice distortions and charge densities, providing a basis for an overall understanding of the low doping phase diagram of La$_{1-x}$Ca$_x$MnO$_3$.