Electronic structure, local magnetism, and spin-orbit effects of Ir(IV)-, Ir(V)-, and Ir(VI)-based compounds

Laguna-Marco, M. A.; Kayser, Paula; Alonso, J. A.; Martı́nez-Lope, M. J.; Veenendaal, Michel van; Choi, Y.; Haskel, D.

doi:10.1103/physrevb.91.214433

Cited by 106 publications

(128 citation statements)

References 52 publications

(30 reference statements)

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“…The experimental branching ratio changes by only 10−12% in going from Ir 4+ to Ir 5+ . 39 Since only less than 25% of Ir ions are in a 5+ valence state at any x value we expect the branching ratio to be rather insensitive to Rh content in agreement with previous reports 28 . The charge transfer from Ir 5d to Rh 4d orbitals via intervening oxygen atoms is consistent with density functional calculations showing that Rh occupied states in the vicinity of the Fermi level (lower Hubbard band) lie lower in energy than Ir 5d occupied states at low Rh doping levels.…”

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confidence: 89%

Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

et al. 2017

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The simultaneous presence of sizable spin-orbit interactions and electron correlations in iridium oxides has led to predictions of novel ground states including Dirac semimetals, Kitaev spin liquids, and superconductivity. Electron and hole doping studies of spin-orbit assisted Mott insulator Sr2IrO4 are being intensively pursued due to extensive parallels with the La2CuO4 parent compound of cuprate superconductors. In particular, the mechanism of charge doping associated with replacement of Ir with Rh ions remains controversial with profound consequences for the interpretation of electronic structure and transport data. Using x-ray absorption near edge structure (XANES) measurements at the Rh L, K-and Ir L-edges we observe anomalous evolution of charge partitioning between Rh and Ir with Rh doping. The partitioning of charge between Rh and Ir sites progresses in a way that holes are initially doped into the J eff =1/2 band at low x only to be removed from it at higher x values. This anomalous hole doping naturally explains the reentrant insulating phase in the phase diagram of Sr2Ir1−xRhxO4 and ought to be considered when searching for superconductivity and other emergent phenomena in iridates doped with 4d elements.

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confidence: 89%

Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

et al. 2017

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“…B. X-ray absorption near edge structure X-ray absorption measurements at the Ir L 2,3 edges as a function of pressure were performed at T = 50 K and 300 K. At very low pressures, the measured BR (BR 50K = 5.5(3), BR 300K = 4.9(3)) strongly deviates from the statistical value of 2 and indicates the presence of strong spin-orbit interaction and proximity to a J eff = 1/2 ground state [48][49][50][51] . Upon further compression, the BR at T = 300 K is essentially constant to at least 2 GPa, after which it monotonically decreases and reduces by ∼ 30% of the initial value at 5.5 GPa, consistent with the opposite behavior displayed by the Ir L 3 and L 2 integrated intensities in Fig.…”

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confidence: 99%

Pressure-induced structural dimerization in the hyperhoneycomb iridateβ−Li2IrO3at low temperatures

et al. 2019

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A pressure-induced collapse of magnetic ordering in β-Li2IrO3 at Pm ∼ 1.5−2 GPa has previously been interpreted as evidence for possible emergence of spin liquid states in this hyperhoneycomb iridate, raising prospects for experimental realizations of the Kitaev model. Based on structural data obtained at room temperature, this magnetic transition is believed to originate in small lattice perturbations that preserve crystal symmetry, and related changes in bond-directional anisotropic exchange interactions. Here we report on the evolution of the crystal structure of β-Li2IrO3 under pressure at low temperatures (T ≤ 50 K) and show that the suppression of magnetism coincides with a change in lattice symmetry involving Ir-Ir dimerization. The critical pressure for dimerization shifts from 4.4(2) GPa at room temperature to ∼ 1.5 − 2 GPa below 50 K. While a direct F ddd → C2/c transition is observed at room temperature, the low temperature transitions involve new as well as coexisting dimerized phases. Further investigation of the Ir (L3/L2) isotropic branching ratio in x-ray absorption spectra indicates that the previously reported departure of the electronic ground state from a J eff = 1/2 state is closely related to the onset of dimerized phases. In essence, our results suggest that the predominant mechanism driving the collapse of magnetism in β-Li2IrO3 is the pressure-induced formation of Ir2 dimers in the hyperhoneycomb network. The results further confirm the instability of the J eff = 1/2 moments and related non-collinear spiral magnetic ordering against formation of dimers in the low-temperature phase of compressed β-Li2IrO3. arXiv:1905.08211v2 [cond-mat.str-el]

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“…The largest component is, as expected, from the S = 3/2 | 4 A 2 state, but the next major contribution is from the S = 1/2 | 2 T 2g state. For ions (5,6,8,9,27).…”

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Spin-Orbit Coupling Controlled J=3/2 Electronic Ground State in 5d3 Oxides

et al. 2017

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Entanglement of spin and orbital degrees of freedom drives the formation of novel quantum and topological physical states. Discovering new spinorbit entangled ground states and emergent phases of matter requires both experimentally probing the relevant energy scales and applying suitable theoretical models. Here we report resonant inelastic x-ray scattering measurements of the transition metal oxides Ca 3 LiOsO 6 and Ba 2 YOsO 6 . We invoke an intermediate coupling approach that incorporates both spin-orbit coupling and electron-electron interactions on an even footing and reveal the ground state of 5d 3 based compounds, which has remained elusive in previously applied models, is a novel spin-orbit entangled J=3/2 electronic ground state. This work reveals the hidden diversity of spin-orbit controlled ground states in 5d systems and introduces a new arena in the search for spin-orbit controlled phases of matter. Main Text:The electronic ground state adopted by an ion is a fundamental determinant of manifested physical properties. Recently, the importance of spin-orbit coupling (SOC) in creating the electronic ground state in 5d-based compounds has come to the fore and arXiv:1610.02375v1 [cond-mat.str-el] systems, and the influence of SOC has now been observed in the macroscopic properties of numerous systems. However, beyond the J eff = 1/2 case such as that found in Sr 2 IrO 4 (3)-which is a single-hole state that applies only to idealised 5d 5 ions in cubic materialsquestions abound concerning the electronic ground states which govern 5d ion interactions.In this context 5d 3 materials present a particularly intriguing puzzle, because octahedral d 3 configurations are expected to be orbitally-quenched S = 3/2 states -in which case SOC enters only as a 3rd order perturbation (4) -yet there is clear experimental evidence that SOC influences the magnetic properties in 5d 3 transition metal oxides (TMOs). This includes the observations of large, SOC-induced spin-gaps in their magnetic excitation spectra (5-7) and x-ray absorption branching ratios which deviate from BR = I L3 /I L2 = 2 (8, 9).Despite this, no description beyond the S = 3/2 state had been established. synchrotron x-ray and neutron diffraction. Figure 1 presents the x-ray energy loss, E, versus incident energy, E i , RIXS spectra of Ca 3 LiOsO 6 at 300 K. Four lines are present at E < 2 eV, which are enhanced at E i = 10.874 keV, whereas the feature at E ≈ 4.5 eV is enhanced at E i = 10.878 keV. This indicates that the E < 2 eV features are intra-t 2g excitations, whereas the higher energy feature is from t 2g to e g excited states, as has been observed in many 5d oxides (7,(18)(19)(20). Subsequent measurements were optimised to probe the t 2g excitations by fixing E i = 10.874 keV.Figure 2 presents the detailed RIXS spectra of Ca 3 LiOsO 6 and Ba 2 YOsO 6 at temperatures of 300 K and 6 K. In each spectrum there are 5 peaks in addition to the elastic line:four peaks with E < 2 eV, labeled a, b, c and d ( Fig. 2c and d) which we associa...

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Electronic structure, local magnetism, and spin-orbit effects of Ir(IV)-, Ir(V)-, and Ir(VI)-based compounds

Cited by 106 publications

References 52 publications

Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

Pressure-induced structural dimerization in the hyperhoneycomb iridateβ−Li2IrO3at low temperatures

Spin-Orbit Coupling Controlled J=3/2 Electronic Ground State in 5d3 Oxides

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