Chemical tuning between triangular and honeycomb structures in a 5$d$ spin-orbit Mott insulator

Abstract

We report structural studies of the spin-orbit Mott insulator family K${}_x$Ir${}_y$O${}_2$, with triangular layers of edge-sharing IrO${}_6$ octahedra bonded by potassium ions. The potassium content acts as a chemical tuning parameter to control the amount of charge in the Ir-O layers. Unlike the isostructural families with Ir replaced by Co or Rh ($y=1$), which are metallic over a range of potassium compositions $x$, we instead find insulating behaviour with charge neutrality achieved via iridium vacancies, which order in a honeycomb supercell above a critical composition $x_c$. By performing density functional theory calculations we attribute the observed behaviour to a subtle interplay of crystal-field environment, local electronic correlations and strong spin-orbit interaction at the Ir${}^{4+}$ sites, making this structural family a candidate to display Kitaev magnetism in the experimentally unexplored regime that interpolates between triangular and honeycomb structures.

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Cited by in corpus (3)

• Effects of charge doping on Mott insulator with strong spin-orbit coupling, Ba${}_2$NaOsO${}_6$
• The ground state in a proximity to a possible Kitaev spin liquid: An undistorted honeycomb iridate NaxIrO3 (0.60 < x < 0.80)
• Topological transition induced by selective random defects on a honeycomb lattice