Spin-orbit coupling driven insulating state in hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li)

TL;DR

This study demonstrates that spin-orbit coupling is the key factor driving the insulating state in hexagonal iridates Sr3MIrO6, with electronic and magnetic properties explained through density functional theory calculations.

Contribution

It reveals the essential role of SOC in inducing insulating states and magnetic behavior in hexagonal iridates, expanding understanding of Jeff states in these materials.

Findings

SOC is the intrinsic source of insulating behavior.

Decreasing IrO6 connectivity increases correlations and SOC effects.

Theoretical results match experimental magnetic properties.

Abstract

The spin-orbit coupling (SOC) interactions, electron correlation effects and Hund coupling cooperate and compete with each other, leading to novel properties, quantum phase and non-trivial topological electronic behavior in iridium oxides. Because of the well separated IrO6 octahedra approaching cubic crystal-field limit, the hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li) serves as a canonical model system to investigate the underlying physical properties that arises from the novel Jeff state. Based on density functional theory calculations complemented by Green's function methods, we systematically explore the critical role of SOC on the electronic structure and magnetic properties of Sr3MIrO6. The crystal-field splitting combined with correlation effects are insufficient to account for the insulating nature, but the SOC interactions is the intrinsic source to trigger the insulating ground states in these hexagonal iridates. The decreasing geometry connectivity of IrO6 octahedra gives rise to the increasing of effective electronic correlations and SOC interactions, tuning the hexagonal iridates from low-spin Jeff = 1/2 states with large local magnetic moments for the Ir4+ (5d5) ions in Sr4IrO6 to nonmagnetic singlet Jeff = 0 states without magnetic moments for the Ir5+ (5d4) ions in Sr3NaIrO6 and Sr3LiIrO6. The theoretical calculated results are in good agreement with available experimental data, and explain the magnetic properties of Sr3MIrO6 well.