Spin-orbit coupling driven insulating state in hexagonal iridates Sr3MIrO6 ( M=Sr

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 IrO 6 octahedra approaching cubic crystal-field limit, the hexagonal iridates Sr 3 MIrO 6 (M = Sr, Na and Li) serves as a canonical model system to investigate the underlying physical properties that arises from the novel J eff 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 Sr 3 MIrO 6 . 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 IrO 6 octahedra gives rise to the increasing of effective electronic correlations and SOC interactions, tuning the hexagonal iridates from low-spin J eff = 1/2 states with large local magnetic moments for the Ir 4+ (5d 5 ) ions in Sr 4 IrO 6 to nonmagnetic singlet J eff = 0 states without magnetic moments for the Ir 5+ (5d 4 ) ions in Sr 3 NaIrO 6 and Sr 3 LiIrO 6 . The theoretical calculated results are in good agreement with available experimental data, and explain the magnetic properties of Sr 3 MIrO 6 well.

Frustration, strain and phase co-existence in the mixed valent hexagonal iridate Ba$_{3}$NaIr$_{2}$O$_{9}$

“…However, the experimentally obtained value is close to the reported magnetic moments 3.6µ B per formula unit for Ba 3 NaIr 2 O 9 and 3.93µ B per formula unit for Ba 3 LiIr 2 O 9 , both having Ir in a similar 5.5 charge state [21]. Such reduction in moment is a peculiar feature seen in iridates and has been reported for a wide range of iridium based oxides [6,[22][23][24].…”

Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^{4}$ magnet

“…Finding this optical mode by increasing the experimental energy range may help to clarify the microscopic understanding of the ground state of Ca 2 RuO 4 . Furthermore, our findings may be of direct relevance for one-dimensional t 4 2g materials, such as OsCl 4 [82] and Sr 3 NaIrO 6 [84]. Especially the later is of interest, because a recent experimental study [83] showed the presence of short-range antiferromagnetic correlations and gapless spin excitations resembling the antiferromagnetic excitonic condensate phase.…”

Correlated motion of particle-hole excitations across the renormalized spin-orbit gap in $\rm Sr_2 Ir O_4$

“…For d 4 systems with nominally n 1 =0, the relative energy shift increases to U − 3J H . This enhancement of the spin-orbit gap renormalization is seen in recent DFT study of the hexagonal iridates Sr 3 LiIrO 6 and Sr IrO 6 with Ir 5+ (5d 4 ) and Ir 4+ (5d 5 ) ions, respectively 25.…”