Hidden Quasiparticles and Incoherent Photoemission Spectra in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Na</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>IrO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>

Trousselet, Fabien; Berciu, Mona; Oleś, Andrzej M.; Horsch, Peter

doi:10.1103/physrevlett.111.037205

Cited by 27 publications

(44 citation statements)

References 52 publications

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“…Hence, we determine the bound state by the divergent condition for Eq. (12). We find that one eigenvalue of Eq.…”

mentioning

confidence: 78%

“…For this reason, much attention has recently been paid to Ir oxides such as Sr 2 IrO 4 1-8 and Na 2 IrO 3 . [9][10][11][12] In particular, we focus on Sr 2 IrO 4 , which consists of two-dimensional IrO 2 layers showing structural similarity to the parent compound of high-T C cuprate La 2 CuO 4 , and exhibits a canted antiferromagnetic (AFM) order below 230 K. [1][2][3] The energy of the e g orbitals is estimated about 2 eV higher than that of the t 2g orbitals due to the large crystal field. Five 5d electrons are occupied per Ir atom, and one hole is sitting in the t 2g orbitals.…”

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confidence: 99%

“…(13) and thereby Eq. (12). Figures 3(a) and (b) show the spectral functions evaluated at the Γ and X points, respectively, with and without Hund's coupling.…”

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confidence: 99%

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Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄

Igarashi

Nagao

2014

J. Phys. Soc. Jpn.

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We study the elementary excitations in 5d transition metal oxide Sr2IrO4 by calculating the particle-hole Green's function within the random phase approximation on an antiferromagnetic ground state in the two-dimensional multi-orbital Hubbard model. The obtained magnetic excitations of bound states show a characteristic dispersion in consistent with the experiments. In addition, two new types of excitations are found due to the interplay between spin-orbit interaction and Hund's coupling: a magnetic excitation as a bound state, which has energy gap at the Γ point, and an exciton as a resonant mode in the continuum of electron-hole pair creation.Electron correlation effects on transition metals and their compounds have attracted much interest since the discovery of high-T C cuprate superconductors. In the 3d transition metal ions, the spin orbit interaction (SOI) plays a minor role on the electronic structures, since it is usually much smaller than the on-site Coulomb interaction and the crystal field splitting. In the 5d transition metal ions, however, the SOI is one order of magnitude larger than that of the 3d systems while the Coulomb interaction becomes weaker due to the extended nature of the 5d electrons. Accordingly, the interplay between the electron correlation and the SOI is expected to bring about new intriguing phenomena. For this reason, much attention has recently been paid to Ir oxides such as Sr 2 IrO 4 1-8 and Na 2 IrO 3 . [9][10][11][12] In particular, we focus on Sr 2 IrO 4 , which consists of two-dimensional IrO 2 layers showing structural similarity to the parent compound of high-T C cuprate La 2 CuO 4 , and exhibits a canted antiferromagnetic (AFM) order below 230 K. 1-3 The energy of the e g orbitals is estimated about 2 eV higher than that of the t 2g orbitals due to the large crystal field. Five 5d electrons are occupied per Ir atom, and one hole is sitting in the t 2g orbitals. Since the hole states have an effective orbital angular momentum ℓ equal to −1, the lowest-energy states on the localized electron picture are doubly degenerate with the effective total angular momentum j eff = 1 2 under the SOI: 13,14 |φ ± = 1 √ 3 (|yz, ∓σ ± i|zx, ∓σ ± |xy, ±σ ), where yz, zx, and xy designate t 2g orbitals, and spin component σ =↑. By introducing the isospin operators acting on these states, the system is mapped onto the Heisenberg model, from which an insulating AFM phase is derived, consistent with the experiments. 1-3 Furthermore, it has been pointed out that the small anisotropic terms emerge in addition to the isotropic term, when Hund's coupling is taken into account in the second-order process in the strong coupling expansion. 15,16 Recently, resonant inelastic x-ray scattering (RIXS) experiment at the Ir L edge has detected the excitation spectra, 17 whose low energy part follows the dispersion relation similar to the spin wave in the Heisenberg model on a square lattice. A notable point is that the excitation energy at the M point is nearly half of that at the X point, in contrast to t...

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“…Hence, we determine the bound state by the divergent condition for Eq. (12). We find that one eigenvalue of Eq.…”

mentioning

confidence: 78%

mentioning

confidence: 99%

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Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄

Igarashi

Nagao

2014

J. Phys. Soc. Jpn.

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“…Hence it was suggested that the numerous simplifications required by the SCBA are in fact too restrictive and a more resilient approach is needed to better understand the effective models of e g systems. Here we make such an attempt via the variational approximation (VA) [10][11][12][13], i.e., solving the equations of motion for the Green function. This method has previously been used by the authors to study a variety of interacting problems, among them an exactly solvable p-d system with FM order, which is a possible model for spin chains in cuprates [14].…”

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confidence: 99%

The Green Function Variational Approximation: Significance of Physical Constraints

2016

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We present a calculation of the spectral properties of a single charge doped at a Cu(3d) site of the Cu-F plane in KCuF3. The problem is treated by generating the equations of motion for the Green function by means of subsequent Dyson expansions and solving the resulting set of equations. This method, dubbed the variational approximation, is both very dependable and flexible, since it is a systematic expansion with precise control over elementary physical processes. It allows for deep insight into the underlying physics of polaron formation as well as for inclusion of many physical constraints, such as excluding crossing diagrams and double occupation constraint, which are not included in the self-consistent Born approximation. Here we examine the role and importance of such constraints by analyzing various spectral functions obtained in second order variational approximation.

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“…This basis is usually very close to the relativistic J ef f =1/2 orbital. [5,16,20,23,24] Superexchange-based formalism is used to describe the zigzag-type AFM ordering. [14,25] The observed PM insulating state well above T N supports the Mott-type mechanism.…”

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confidence: 99%

Insulating nature ofNa2IrO3: Mott-type or Slater-type

Kim

Min

2016

Phys. Rev. B

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We have investigated temperature-dependent electronic structures of Na2IrO3 to unravel its insulating nature. Employing the combined scheme of the density-functional theory (DFT) and the dynamical mean-field theory (DMFT), we have shown that the insulating state persists even above the Néel temperature (TN ), which reveals that Na2IrO3 is classified into a Mott-type insulator. The measured photoemission spectrum in the paramagnetic (PM) state is well described by the electronic structure obtained from the DFT+DMFT for the insulating state above TN . The analysis of optical conductivity, however, suggests that the non-local correlation effect is also important in Na2IrO3. Therefore, Na2IrO3 is not to be a standard Mott insulator in that the extended nature and the non-local correlation effect of Ir 5d electrons are important as well in describing its electronic and magnetic properties.PACS numbers: 75.47. Lx, 71.70.Ej Identifying the insulating nature of transition metal oxides has been a central and long-standing subject in modern condensed matter physics.[1] Recent attention has been paid to 5d transition metal oxides, Sr 2 IrO 4 and Na 2 IrO 3 , whether they belong to Mott-type or Slatertype insulators. The strong spin-orbit coupling (SOC) and the rather weak Coulomb correlation of 5d electrons are known to be two essential ingredients in determining the ground state physics of Sr 2 IrO 4 and Na 2 IrO 3 .[2-21] Despite intense studies on the role of interplay between Coulomb interaction and SOC, however, there has been no consensus on the nature of their insulating states yet. For example, on the insulating nature of Sr 2 IrO 4 , there exist two contradictory reports, Mott insulator [6] vs. Slater insulator. [7] A marginal Mott insulating state was also proposed, in which the insulating state above the Néel temperature (T N =240 K) was attributed to the presence of short range antiferromagnetic (AFM) correlation. [9,15] For Na 2 IrO 3 too, which is a system of our present interest, there have been debates on its insulating nature. [11][12][13][14][17][18][19][20][21] Na 2 IrO 3 exhibits insulating state at room temperature (T ), well above T N =15 K. [11,12] The paramagnetic (PM) state with Curie-Weiss susceptibility behavior was confirmed up to T = 500 K.[12] The zigzag-type AFM ordering occurs below T N . [8,22] To explain the AFM insulating ground state of Na 2 IrO 3 , both the Motttype [11,17] and Slater-type [13,18,19,21] mechanisms of the metal-insulator transition were invoked. In the former, the good basis to describe the local electronic structure is derived by consideration of the on-site atomic SOC and the crystal field. This basis is usually very close to the relativistic J ef f =1/2 orbital. [5,16,20,23,24] Superexchange-based formalism is used to describe the zigzag-type AFM ordering. [14,25] The observed PM insulating state well above T N supports the Mott-type mechanism.[11] In the Mott-type mechanism, however, very long range magnetic interaction or very high energy excitation is required t...

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Hidden Quasiparticles and Incoherent Photoemission Spectra inNa2IrO3

Cited by 27 publications

References 52 publications

Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄

Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄

The Green Function Variational Approximation: Significance of Physical Constraints

Insulating nature ofNa2IrO3: Mott-type or Slater-type

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Hidden Quasiparticles and Incoherent Photoemission Spectra inNa2IrO3

Cited by 27 publications

References 52 publications

Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr2IrO4

Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr2IrO4

The Green Function Variational Approximation: Significance of Physical Constraints

Insulating nature ofNa2IrO3: Mott-type or Slater-type

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Product

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Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄

Interplay between Hund’s Coupling and Spin–Orbit Interaction on Elementary Excitations in Sr₂IrO₄