1
|
Lu C, Liu JM. The J eff = 1/2 Antiferromagnet Sr 2 IrO 4 : A Golden Avenue toward New Physics and Functions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1904508. [PMID: 31667943 DOI: 10.1002/adma.201904508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 09/12/2019] [Indexed: 06/10/2023]
Abstract
Iridates have been providing a fertile ground for studying emergent phases of matter that arise from the delicate interplay of various fundamental interactions with approximate energy scale. Among these highly focused quantum materials, the perovskite Sr2 IrO4 , which belongs to the Ruddlesden-Popper series, stands out and has been intensively addressed in the last decade, since it hosts a novel Jeff = 1/2 state that is a profound manifestation of strong spin-orbit coupling. Moreover, the Jeff = 1/2 state represents a rare example of iridates that is better understood both theoretically and experimentally. Here, Sr2 IrO4 is taken as an example to review the recent advances of the Jeff = 1/2 state in two aspects: materials fundamentals and functionality potentials. In the fundamentals part, the basic issues for the layered canted antiferromagnetic order of the Jeff = 1/2 magnetic moments in Sr2 IrO4 are illustrated, and then the progress of the antiferromagnetic order modulation through diverse routes is highlighted. Subsequently, for the functionality potentials, fascinating properties such as atomic-scale giant magnetoresistance, anisotropic magnetoresistance, and nonvolatile memory, are addressed. To conclude, prospective remarks and an outlook are given.
Collapse
Affiliation(s)
- Chengliang Lu
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Jun-Ming Liu
- Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials and Institute for Advanced Materials, South China Normal University, Guangzhou, 510006, China
| |
Collapse
|
2
|
Interfacial charge-transfer Mott state in iridate-nickelate superlattices. Proc Natl Acad Sci U S A 2019; 116:19863-19868. [PMID: 31527227 DOI: 10.1073/pnas.1907043116] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We investigate [Formula: see text]/[Formula: see text] superlattices in which we observe a full electron transfer at the interface from Ir to Ni, triggering a massive structural and electronic reconstruction. Through experimental characterization and first-principles calculations, we determine that a large crystal field splitting from the distorted interfacial [Formula: see text] octahedra surprisingly dominates over the spin-orbit coupling and together with the Hund's coupling results in the high-spin (S = 1) configurations on both the Ir and Ni sites. This demonstrates the power of interfacial charge transfer in coupling lattice, charge, orbital, and spin degrees of freedom, opening fresh avenues of investigation of quantum states in oxide superlattices.
Collapse
|
3
|
Lenz B, Martins C, Biermann S. Spectral functions of Sr 2IrO 4: theory versus experiment. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:293001. [PMID: 30921786 DOI: 10.1088/1361-648x/ab146a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The spin-orbit Mott insulator Sr2IrO4 has attracted a lot of interest in recent years from theory and experiment due to its close connection to isostructural high-temperature copper oxide superconductors. Despite not being superconductive, its spectral features closely resemble those of the cuprates, including Fermi surface and pseudogap properties. In this article, we review and extend recent work in the theoretical description of the spectral function of pure and electron-doped Sr2IrO4 based on a cluster extension of dynamical mean-field theory ('oriented-cluster DMFT') and compare it to available angle-resolved photoemission data. Current theories provide surprisingly good agreement for pure and electron-doped Sr2IrO4, both in the paramagnetic and antiferromagnetic phases. Most notably, one obtains simple explanations for the experimentally observed steep feature around the M point and the pseudo-gap-like spectral feature in electron-doped Sr2IrO4.
Collapse
Affiliation(s)
- B Lenz
- CPHT, Ecole Polytechnique, CNRS, Université Paris-Saclay, Route de Saclay, 91128 Palaiseau, France
| | | | | |
Collapse
|
4
|
Liu H, Khaliullin G. Pseudo-Jahn-Teller Effect and Magnetoelastic Coupling in Spin-Orbit Mott Insulators. PHYSICAL REVIEW LETTERS 2019; 122:057203. [PMID: 30822030 DOI: 10.1103/physrevlett.122.057203] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 11/22/2018] [Indexed: 06/09/2023]
Abstract
The consequences of the Jahn-Teller (JT) orbital-lattice coupling for magnetism of pseudospin J_{eff}=1/2 and J_{eff}=0 compounds are addressed. In the former case, represented by Sr_{2}IrO_{4}, this coupling generates, through the so-called pseudo-JT effect, orthorhombic deformations of a crystal concomitant with magnetic ordering. The orthorhombicity axis is tied to the magnetization and rotates with it under magnetic field. The theory resolves a number of puzzles in Sr_{2}IrO_{4} such as the origin of in-plane magnetic anisotropy and magnon gaps, metamagnetic transition, etc. In J_{eff}=0 systems, the pseudo-JT effect leads to spin-nematic transition well above magnetic ordering, which may explain the origin of "orbital order" in Ca_{2}RuO_{4}.
Collapse
Affiliation(s)
- Huimei Liu
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Giniyat Khaliullin
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| |
Collapse
|
5
|
Wang Y, Weng H, Fu L, Dai X. Noncollinear Magnetic Structure and Multipolar Order in Eu_{2}Ir_{2}O_{7}. PHYSICAL REVIEW LETTERS 2017; 119:187203. [PMID: 29219540 DOI: 10.1103/physrevlett.119.187203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Indexed: 06/07/2023]
Abstract
The magnetic properties of the pyrochlore iridate material Eu_{2}Ir_{2}O_{7} (5d^{5}) have been studied based on first principles calculations, where the crystal field splitting Δ, spin-orbit coupling (SOC) λ, and Coulomb interaction U within Ir 5d orbitals all play significant roles. The ground state phase diagram has been obtained with respect to the strength of SOC and Coulomb interaction U, where a stable antiferromagnetic ground state with all-in-all-out (AIAO) spin structure has been found. In addition, another antiferromagnetic state with energy close to AIAO has also been found to be stable. The calculated nonlinear magnetization of the two stable states both have the d-wave pattern but with a π/4 phase difference, which can perfectly explain the experimentally observed nonlinear magnetization pattern. Compared with the results of the nondistorted structure, it turns out that the trigonal lattice distortion is crucial for stabilizing the AIAO state in Eu_{2}Ir_{2}O_{7}. Furthermore, besides large dipolar moments, we also find considerable octupolar moments in the magnetic states.
Collapse
Affiliation(s)
- Yilin Wang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Xi Dai
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| |
Collapse
|
6
|
Martins C, Aichhorn M, Biermann S. Coulomb correlations in 4d and 5d oxides from first principles-or how spin-orbit materials choose their effective orbital degeneracies. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:263001. [PMID: 28262638 DOI: 10.1088/1361-648x/aa648f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The interplay of spin-orbit coupling and Coulomb correlations has become a hot topic in condensed matter theory and is especially important in 4d and 5d transition metal oxides, like iridates or rhodates. Here, we review recent advances in dynamical mean-field theory (DMFT)-based electronic structure calculations for treating such compounds, introducing all necessary implementation details. We also discuss the evaluation of Hubbard interactions in spin-orbit materials. As an example, we perform DMFT calculations on insulating strontium iridate (Sr2IrO4) and its 4d metallic counterpart, strontium rhodate (Sr2RhO4). While a Mott-insulating state is obtained for Sr2IrO4 in its paramagnetic phase, the spectral properties and Fermi surfaces obtained for Sr2RhO4 show excellent agreement with available experimental data. Finally, we discuss the electronic structure of these two compounds by introducing the notion of effective spin-orbital degeneracy as the key quantity that determines the correlation strength. We stress that effective spin-orbital degeneracy introduces an additional axis into the conventional picture of a phase diagram based on filling and on the ratio of interactions to bandwidth, analogous to the degeneracy-controlled Mott transition in d1 perovskites.
Collapse
Affiliation(s)
- C Martins
- Laboratoire de Chimie et Physique Quantiques, UMR 5626, Université Paul Sabatier, 118 route de Narbonne, 31400 Toulouse, France
| | | | | |
Collapse
|
7
|
Zhang H, Haule K, Vanderbilt D. Metal-Insulator Transition and Topological Properties of Pyrochlore Iridates. PHYSICAL REVIEW LETTERS 2017; 118:026404. [PMID: 28128605 DOI: 10.1103/physrevlett.118.026404] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 06/06/2023]
Abstract
Combining density functional theory (DFT) and embedded dynamical mean-field theory (DMFT) methods, we study the metal-insulator transition in R_{2}Ir_{2}O_{7} (R=Y, Eu, Sm, Nd, Pr, and Bi) and the topological nature of the insulating compounds. Accurate free energies evaluated using the charge self-consistent DFT+DMFT method reveal that the metal-insulator transition occurs for an A-cation radius between that of Nd and Pr, in agreement with experiments. The all-in-all-out magnetic phase, which is stable in the Nd compound but not the Pr one, gives rise to a small Ir^{4+} magnetic moment of ≈0.4 μ_{B} and opens a sizable correlated gap. We demonstrate that within this state-of-the-art theoretical method, the insulating bulk pyrochlore iridates are topologically trivial.
Collapse
Affiliation(s)
- Hongbin Zhang
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
- Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany
| | - Kristjan Haule
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - David Vanderbilt
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| |
Collapse
|
8
|
Krupin O, Dakovski GL, Kim BJ, Kim JW, Kim J, Mishra S, Chuang YD, Serrao CR, Lee WS, Schlotter WF, Minitti MP, Zhu D, Fritz D, Chollet M, Ramesh R, Molodtsov SL, Turner JJ. Ultrafast dynamics of localized magnetic moments in the unconventional Mott insulator Sr2IrO4. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:32LT01. [PMID: 27310659 DOI: 10.1088/0953-8984/28/32/32lt01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report a time-resolved study of the ultrafast dynamics of the magnetic moments formed by the [Formula: see text] states in Sr2IrO4 by directly probing the localized iridium 5d magnetic state through resonant x-ray diffraction. Using optical pump-hard x-ray probe measurements, two relaxation time scales were determined: a fast fluence-independent relaxation is found to take place on a time scale of 1.5 ps, followed by a slower relaxation on a time scale of 500 ps-1.5 ns.
Collapse
Affiliation(s)
- O Krupin
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA 94720, USA. European XFEL, Hamburg 22761, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Pedersen KS, Bendix J, Tressaud A, Durand E, Weihe H, Salman Z, Morsing TJ, Woodruff DN, Lan Y, Wernsdorfer W, Mathonière C, Piligkos S, Klokishner SI, Ostrovsky S, Ollefs K, Wilhelm F, Rogalev A, Clérac R. Iridates from the molecular side. Nat Commun 2016; 7:12195. [PMID: 27435800 PMCID: PMC4961767 DOI: 10.1038/ncomms12195] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/07/2016] [Indexed: 11/09/2022] Open
Abstract
New exotic phenomena have recently been discovered in oxides of paramagnetic Ir4+ ions, widely known as ‘iridates'. Their remarkable properties originate from concerted effects of the crystal field, magnetic interactions and strong spin-orbit coupling, characteristic of 5d metal ions. Despite numerous experimental reports, the electronic structure of these materials is still challenging to elucidate, and not attainable in the isolated, but chemically inaccessible, [IrO6]8– species (the simplest molecular analogue of the elementary {IrO6}8− fragment present in all iridates). Here, we introduce an alternative approach to circumvent this problem by substituting the oxide ions in [IrO6]8− by isoelectronic fluorides to form the fluorido-iridate: [IrF6]2−. This molecular species has the same electronic ground state as the {IrO6}8− fragment, and thus emerges as an ideal model for iridates. These results may open perspectives for using fluorido-iridates as building-blocks for electronic and magnetic quantum materials synthesized by soft chemistry routes. Iridates are known to exhibit a range of exotic electronic and magnetic behaviours but it is difficult to prepare isolated [IrO6]8− species via soft chemical routes. Here, the authors isolate the isoelectronic [IrF6]2− complex, and assess it as a model and for iridate analogues.
Collapse
Affiliation(s)
- Kasper S Pedersen
- CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, CRPP, UPR 8641, Pessac 33600, France.,CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, ICMCB, UPR 9048, Pessac 33600, France
| | - Jesper Bendix
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Alain Tressaud
- CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, ICMCB, UPR 9048, Pessac 33600, France
| | - Etienne Durand
- CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, ICMCB, UPR 9048, Pessac 33600, France
| | - Høgni Weihe
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Zaher Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen PSI CH-5232, Switzerland
| | - Thorbjørn J Morsing
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | | | - Yanhua Lan
- CNRS, Inst NEEL, Grenoble F-38000, France
| | | | - Corine Mathonière
- CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, ICMCB, UPR 9048, Pessac 33600, France
| | - Stergios Piligkos
- Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark
| | - Sophia I Klokishner
- Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev 2028, Moldova
| | - Serghei Ostrovsky
- Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev 2028, Moldova
| | - Katharina Ollefs
- ESRF - The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France
| | - Fabrice Wilhelm
- ESRF - The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France
| | - Andrei Rogalev
- ESRF - The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9, France
| | - Rodolphe Clérac
- CNRS, ICMCB, UPR 9048, Pessac 33600, France.,Univ. Bordeaux, CRPP, UPR 8641, Pessac 33600, France
| |
Collapse
|
10
|
Bogdanov NA, Katukuri VM, Romhányi J, Yushankhai V, Kataev V, Büchner B, van den Brink J, Hozoi L. Orbital reconstruction in nonpolar tetravalent transition-metal oxide layers. Nat Commun 2015; 6:7306. [PMID: 26105992 PMCID: PMC4491190 DOI: 10.1038/ncomms8306] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 04/27/2015] [Indexed: 01/07/2023] Open
Abstract
A promising route to tailoring the electronic properties of quantum materials and devices rests on the idea of orbital engineering in multilayered oxide heterostructures. Here we show that the interplay of interlayer charge imbalance and ligand distortions provides a knob for tuning the sequence of electronic levels even in intrinsically stacked oxides. We resolve in this regard the d-level structure of layered Sr2IrO4 by electron spin resonance. While canonical ligand-field theory predicts g||-factors less than 2 for positive tetragonal distortions as present in Sr2IrO4, the experiment indicates g|| is greater than 2. This implies that the iridium d levels are inverted with respect to their normal ordering. State-of-the-art electronic-structure calculations confirm the level switching in Sr2IrO4, whereas we find them in Ba2IrO4 to be instead normally ordered. Given the nonpolar character of the metal-oxygen layers, our findings highlight the tetravalent transition-metal 214 oxides as ideal platforms to explore d-orbital reconstruction in the context of oxide electronics. The iridate compounds display interesting physical properties, including quasi-two-dimensional behaviour similar to cuprates. Bogdanov et al. explore the d-level structure of Sr2IrO4 using electron spin resonance measurements and detailed calculations and find it is inverted compared to its normal ordering
Collapse
Affiliation(s)
- Nikolay A Bogdanov
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Vamshi M Katukuri
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Judit Romhányi
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Viktor Yushankhai
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Russia
| | - Vladislav Kataev
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - Bernd Büchner
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Department of Physics, Technical University Dresden, 01062 Dresden, Germany
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany.,Department of Physics, Technical University Dresden, 01062 Dresden, Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| |
Collapse
|
11
|
Birol T, Haule K. J(eff)=1/2 Mott-insulating state in Rh and Ir fluorides. PHYSICAL REVIEW LETTERS 2015; 114:096403. [PMID: 25793833 DOI: 10.1103/physrevlett.114.096403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Indexed: 06/04/2023]
Abstract
Discovery of new transition metal compounds with large spin orbit coupling coexisting with strong electron-electron correlation among the d electrons is essential for understanding the physics that emerges from the interplay of these two effects. In this study, we predict a novel class of J_{eff}=1/2 Mott insulators in a family of fluoride compounds that are previously synthesized, but not characterized extensively. First principles calculations in the level of all electron density functional theory+dynamical mean field theory indicate that these compounds have large Mott gaps and some of them exhibit unprecedented proximity to the ideal, SU(2) symmetric J_{eff}=1/2 limit.
Collapse
Affiliation(s)
- Turan Birol
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Kristjan Haule
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| |
Collapse
|
12
|
Kim J, Daghofer M, Said AH, Gog T, van den Brink J, Khaliullin G, Kim BJ. Excitonic quasiparticles in a spin–orbit Mott insulator. Nat Commun 2014; 5:4453. [DOI: 10.1038/ncomms5453] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 06/19/2014] [Indexed: 11/09/2022] Open
|