Metal-insulator transition and topological properties of pyrochlore iridates

TL;DR

This study combines advanced computational methods to analyze the metal-insulator transition and topological properties of pyrochlore iridates, revealing the transition point and trivial topological nature of the insulating phases.

Contribution

It provides a detailed theoretical analysis of the metal-insulator transition and topological characteristics of $R_2$Ir$_2$O$_7$ compounds using DFT+DMFT methods, aligning with experimental data.

Findings

Transition occurs between Nd and Pr cation radii.

All-in-all-out magnetic phase induces a small magnetic moment and opens a gap.

Insulating pyrochlore iridates are topologically trivial.

Abstract

Combining density functional theory (DFT) and embedded dynamical mean-field theory (DMFT) methods, we study the metal-insulator transition in $R_2$Ir$_2$O$_7$ ($R$=Y, Eu, Sm, Nd, Pr, and Bi) and the topological nature of the insulating compounds. Accurate free energies evaluated using the charge self-consistent DFT+DMFT method reveal that the metal-insulator transition occurs for an A-cation radius between that of Nd and Pr, in agreement with experiments. The all-in-all-out magnetic phase, which is stable in the Nd compound but not the Pr one, gives rise to a small Ir$^{4+}$ magnetic moment of $\approx 0.5\mu_B$ and opens a sizable correlated gap. We demonstrate that within this state-of-the-art theoretical method, the insulating bulk pyrochlore iridates are topologically trivial.