Suppressed Coherence due to Orbital Correlations in the Ferromagnetically Ordered Metallic Phase of Mn Compounds

TL;DR

This paper investigates the suppressed coherence in the ferromagnetic metallic phase of Mn compounds, attributing it to orbital correlations and proximity to a Mott insulator, supported by scaling theory and experimental data.

Contribution

It introduces a scaling theory linking orbital correlations to suppressed coherence and explains experimental observations in Mn compounds.

Findings

Small Drude weight and specific heat coefficient explained by proximity to Mott insulator.

Orbital correlations lead to critical exponents for conductivity and heat capacity.

Scaling theory matches experimental data on Mn compounds.

Abstract

Small Drude weight $D$ together with small specific heat coefficient $\gamma$ observed in the ferromagnetic phase of R$_{1-x}$A$_x$MnO$_3$ (R=La, Pr, Nd, Sm; A=Ca, Sr, Ba) are analyzed in terms of a proximity effect of the Mott insulator. The scaling theory for the metal-insulator transition with the critical enhancement of orbital correlations toward the staggered ordering of two $e_g$ orbitals such as $3x^2-r^2$ and $3y^2-r^2$ symmetries may lead to the critical exponents of $D \propto \delta^{u}$ and $\gamma \propto \delta^v$ with $u=3/2$ and $v=0$. The result agrees with the experimental indications.