Charge transfer energy in iridates: a hard x-ray photoelectron spectroscopy study

Abstract

We have investigated the electronic structure of iridates in the double perovskite crystal structure containing either Ir${}^{4+}$ or Ir${}^{5+}$ using hard x-ray photoelectron spectroscopy. The experimental valence band spectra can be well reproduced using tight binding calculations including only the Ir $5d$, O $2p$ and O $2s$ orbitals with parameters based on the downfolding of the density-functional band structure results. We found that regardless of the A and B cations, the A${}_2$BIrO${}_6$ iridates have essentially zero O $2p$ to Ir $5d$ charge transfer energies. Hence, double perovskite iridates turn out to be extremely covalent systems with the consequence being that the magnetic exchange interactions become very long-ranged, thereby hampering the materialization of the long-sought Kitaev physics. Nevertheless, it still would be possible to realize a spin-liquid system using the iridates with a proper tuning of the various competing exchange interactions.

9 pages, 7 figures, submitted to Physical Review B

References in corpus (5)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Models and Materials for Generalized Kitaev Magnetism
• Magnetism and spin-orbit coupling in Ir-based double perovskites La${}_{(}2-x$Sr${}_x$CoIrO${}_6$
• Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates

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• Gapless dynamic magnetic ground state in the charge-gapped trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Novel quantum spin liquid ground state in the trimer rhodate Ba${}_4$NbRh${}_3$O${}_{12}$
• The 3d and 5d electronic structures and orbital hybridization in Ba- and Ca-doped La2CoIrO6 double perovskite
• Yb 4f-Ta 5d Hybridization and Valence Evolution in Tetragonal Tungsten Bronze Ba(3-x)YbxTa5O15