{\it Ab initio} Studies on the Interplay between Spin-Orbit Interaction and Coulomb Correlation in Sr$_2$IrO$_4$ and Ba$_2$IrO$_4$

TL;DR

This study uses ab initio methods to analyze how spin-orbit interaction and Coulomb correlation influence the electronic phases of Sr$_2$IrO$_4$ and Ba$_2$IrO$_4$, revealing their classification as Slater insulators with a complex gap formation mechanism.

Contribution

It provides a detailed ab initio analysis of the interplay between spin-orbit coupling and electron correlations in iridates, demonstrating their Slater insulator nature and the role of magnetic order and band renormalization.

Findings

Correctly reproduces metal-insulator transitions in Sr and Ba iridates.

Classifies these compounds as Slater insulators, not Mott insulators.

Identifies the synergy of magnetic order and band effects in gap opening.

Abstract

{\it Ab initio} analyses of A$_2$IrO$_4$ (A=Sr, Ba) are presented. Effective Hubbard-type models for Ir 5$d$ $t_{2g}$ manifolds downfolded from the global band structure are solved based on the dynamical mean-field theory. The results for A=Sr and Ba correctly reproduce paramagnetic metals undergoing continuous transitions to insulators below the N\'eel temperature $T_N$. These compounds are classified not into Mott insulators but into Slater insulators. However, the insulating gap opens by a synergy of the Neel order and significant band renormalization, which is also manifested by a 2D bad metallic behavior in the paramagnetic phase near the quantum criticality.