Randomly Diluted e_g Orbital-Ordered Systems

TL;DR

This paper investigates how dilution with impurities affects the orbital order in e_g orbital systems, revealing a significant decrease in ordering temperature and unique tilting effects, with implications for experimental observations in KCu$_{1-x}$Zn$_x$F$_3$.

Contribution

It introduces a novel analysis of dilution effects on orbital order using Monte-Carlo and cluster-expansion methods, highlighting the role of orbital tilting around impurities.

Findings

Dilution causes a remarkable decrease in orbital ordering temperature.

Orbital tiltings around impurities are key to the unique dilution effects.

The theory explains recent experimental results in KCu$_{1-x}$Zn$_x$F$_3$.

Abstract

Dilution effects on the long-range ordered state of the doubly degenerate $e_g$ orbital are investigated. Quenched impurities without the orbital degree of freedom are introduced in the orbital model where the long-range order is realized by the order-from-disorder mechanism. It is shown by the Monte-Carlo simulation and the cluster-expansion method that a decrease in the orbital ordering temperature by dilution is remarkable in comparison with that in the randomly diluted spin models. Tiltings of orbitals around impurity cause this unique dilution effects on the orbital systems. The present theory provides a new view point for the recent experiments in KCu$_{1-x}$Zn$_x$F$_3$.