Electron interactions, spin-orbit coupling, intersite correlations in pyrochlore iridates

TL;DR

This study combines advanced computational methods to explore the complex electronic and magnetic phases of pyrochlore iridates, revealing the crucial role of intersite correlations in their properties.

Contribution

It demonstrates that single-site dynamical mean-field theory fails to capture key material differences, emphasizing the importance of intersite correlations in these compounds.

Findings

Identification of paramagnetic, metallic, and insulating phases.

Discovery of all-in/all-out magnetic ordering.

Failure of single-site DMFT to predict material differences.

Abstract

We perform combined density functional and dynamical mean-field calculations to study the pyrochlore iridates Lu$_2$Ir$_2$O$_7$, Y$_2$Ir$_2$O$_7$ and Eu$_2$Ir$_2$O$_7$. Both single-site and cluster dynamical mean-field calculations are performed and spin-orbit coupling is included. Paramagnetic metallic phases, antiferromagnetic metallic phases with tilted Weyl cones and antiferromagnetic insulating phases are found. The magnetic phases display all-in/all-out magnetic ordering, consistent with previous studies. Unusually for electronically three dimensional materials, the single-site dynamical mean-field approximation fails to reproduce qualitative material trends, predicting in particular that the paramagnetic phase properties of Y$_2$Ir$_2$O$_7$ and Eu$_2$Ir$_2$O$_7$ are almost identical, although in experiments the Y compound has a much higher resistance than the Eu compound. This qualitative failure is attributed to the importance of intersite magnetic correlations in the physics of these materials.