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Chen HY, Versteeg RB, Mankowsky R, Puppin M, Leroy L, Sander M, Deng Y, Oggenfuss RA, Zamofing T, Böhler P, Pradervand C, Mozzanica A, Vetter S, Smolentsev G, Kerkhoff L, Lemke HT, Chergui M, Mancini GF. A setup for hard x-ray time-resolved resonant inelastic x-ray scattering at SwissFEL. Struct Dyn 2024; 11:024308. [PMID: 38586277 PMCID: PMC10998714 DOI: 10.1063/4.0000236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 03/04/2024] [Indexed: 04/09/2024]
Abstract
We present a new setup for resonant inelastic hard x-ray scattering at the Bernina beamline of SwissFEL with energy, momentum, and temporal resolution. The compact R = 0.5 m Johann-type spectrometer can be equipped with up to three crystal analyzers and allows efficient collection of RIXS spectra. Optical pumping for time-resolved studies can be realized with a broad span of optical wavelengths. We demonstrate the performance of the setup at an overall ∼180 meV resolution in a study of ground-state and photoexcited (at 400 nm) honeycomb 5d iridate α-Li2IrO3. Steady-state RIXS spectra at the iridium L3-edge (11.214 keV) have been collected and are in very good agreement with data collected at synchrotrons. The time-resolved RIXS transients exhibit changes in the energy loss region <2 eV, whose features mostly result from the hopping nature of 5d electrons in the honeycomb lattice. These changes are ascribed to modulations of the Ir-to-Ir inter-site transition scattering efficiency, which we associate to a transient screening of the on-site Coulomb interaction.
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Affiliation(s)
- Hui-Yuan Chen
- Lausanne Centre for Ultrafast Science (LACUS), ISIC, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Rolf B. Versteeg
- Lausanne Centre for Ultrafast Science (LACUS), ISIC, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Roman Mankowsky
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Michele Puppin
- Lausanne Centre for Ultrafast Science (LACUS), ISIC, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | | | - Mathias Sander
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Yunpei Deng
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | | | - Thierry Zamofing
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Pirmin Böhler
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Claude Pradervand
- Photon Science Division, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Aldo Mozzanica
- Photon Science Division, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Seraphin Vetter
- Photon Science Division, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Grigory Smolentsev
- Energy and Environment Research Division, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Linda Kerkhoff
- Sect. Crystallography, Institute of Geology and Mineralogy, University of Cologne, 50674 Köln, Germany
| | - Henrik T. Lemke
- SwissFEL, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
| | - Majed Chergui
- Authors to whom correspondence should be addressed: and
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2
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Sun Y, Jiang Z, Li Y, Liu L, Liang H, Wang Y, Wu D, Li N, Zhou Y, Li Q, Yue X, Tong W, Luo X, Lan J, Sun X. Observation of the possible magnetic correction above the Curie temperature in Cr 2Si 2Te 6 single crystals. Phys Chem Chem Phys 2024; 26:1396-1405. [PMID: 38112118 DOI: 10.1039/d3cp03854h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Intrinsic magnetic semiconductors hold great promise in the fields of fundamental magnetization and spintronics. One such semiconductor is Cr2Si2Ti6 (CST), a quasi two-dimensional (2D) magnetic semiconductor with potential applications in future magnetic devices. However, the origin of ferromagnetism in CST remains a mystery. To investigate this, ac/dc susceptibility and electronic spin resonance (ESR) measurements were conducted. Based on ac susceptibility scaling, the critical temperature (TC) for the ferromagnetic (FM) to paramagnetic (PM) phase transition was found to be ∼32.5 K, with a critical exponent of δ = 6.7 from the critical isotherm, β + γ = 1.72 from the temperature dependence of the crossover line, and γ = 1.43 from the temperature dependence of susceptibility along the same line. All critical exponents were found to be consistent with the dc magnetization scaling method. However, above and below TC, the origin of magnetism cannot be explained by a single theory. To explore the origin of abnormal magnetic critical behavior, ESR measurements were performed. Below T* ∼ 130 K, the ESR measurements revealed that the resonance field width (ΔH) tends to increase and decrease for the applied magnetic field H parallel and perpendicular to the c axis, respectively, indicating the onset of magnetic interaction even in the PM state. Meanwhile, the deviation from Curie-Weiss behavior below T* also confirmed the occurrence of magnetic correlation above the TC in CST. These observations suggest that the competition and cooperation among the direct and indirect interactions, the structural distortion and the van der Waals interaction at high temperature should be considered to investigate the origin of anomalous magnetism in CST. The present results provide valuable insights into the nature of ferromagnetism in 2D magnetic semiconductors.
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Affiliation(s)
- Yan Sun
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Zhongzhu Jiang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Yang Li
- Southwest Institute of Applied Magnetics, Mianyang 621000, P. R. China.
| | - Lanxin Liu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Hui Liang
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Yiyan Wang
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Dandan Wu
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Na Li
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Ying Zhou
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
| | - Qiuju Li
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei, Anhui 230601, P. R. China
| | - Xiaoyu Yue
- School of Optical and Electronic Information, Suzhou City University, Suzhou 215104, P. R. China
| | - Wei Tong
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Xuan Luo
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Jianghe Lan
- Southwest Institute of Applied Magnetics, Mianyang 621000, P. R. China.
| | - Xuefeng Sun
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China.
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3
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de la Torre A, Zager B, Bahrami F, Upton MH, Kim J, Fabbris G, Lee GH, Yang W, Haskel D, Tafti F, Plumb KW. Momentum-independent magnetic excitation continuum in the honeycomb iridate H 3LiIr 2O 6. Nat Commun 2023; 14:5018. [PMID: 37596328 PMCID: PMC10439105 DOI: 10.1038/s41467-023-40769-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 08/07/2023] [Indexed: 08/20/2023] Open
Abstract
Understanding the interplay between the inherent disorder and the correlated fluctuating-spin ground state is a key element in the search for quantum spin liquids. H3LiIr2O6 is considered to be a spin liquid that is proximate to the Kitaev-limit quantum spin liquid. Its ground state shows no magnetic order or spin freezing as expected for the spin liquid state. However, hydrogen zero-point motion and stacking faults are known to be present. The resulting bond disorder has been invoked to explain the existence of unexpected low-energy spin excitations, although data interpretation remains challenging. Here, we use resonant X-ray spectroscopies to map the collective excitations in H3LiIr2O6 and characterize its magnetic state. In the low-temperature correlated state, we reveal a broad bandwidth of magnetic excitations. The central energy and the high-energy tail of the continuum are consistent with expectations for dominant ferromagnetic Kitaev interactions between dynamically fluctuating spins. Furthermore, the absence of a momentum dependence to these excitations are consistent with disorder-induced broken translational invariance. Our low-energy data and the energy and width of the crystal field excitations support an interpretation of H3LiIr2O6 as a disordered topological spin liquid in close proximity to bond-disordered versions of the Kitaev quantum spin liquid.
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Affiliation(s)
- A de la Torre
- Department of Physics, Brown University, Providence, RI, 02912, USA.
| | - B Zager
- Department of Physics, Brown University, Providence, RI, 02912, USA
| | - F Bahrami
- Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA
| | - M H Upton
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - J Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - G Fabbris
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - G-H Lee
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, 94720, USA
| | - W Yang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, 94720, USA
| | - D Haskel
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - F Tafti
- Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA
| | - K W Plumb
- Department of Physics, Brown University, Providence, RI, 02912, USA.
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4
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Bahrami F, Hu X, Du Y, Lebedev OI, Wang C, Luetkens H, Fabbris G, Graf MJ, Haskel D, Ran Y, Tafti F. First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice. Sci Adv 2022; 8:eabl5671. [PMID: 35319975 PMCID: PMC8942356 DOI: 10.1126/sciadv.abl5671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 02/01/2022] [Indexed: 06/02/2023]
Abstract
Recent observations of novel spin-orbit coupled states have generated interest in 4d/5d transition metal systems. A prime example is the [Formula: see text] state in iridate materials and α-RuCl3 that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (λSOC) and trigonal crystal field (ΔT), we restructure the spin-orbital wave functions into a previously unobserved [Formula: see text] state that drives Ising interactions. This is done via a topochemical reaction that converts Li2RhO3 to Ag3LiRh2O6. Using perturbation theory, we present an explicit expression for the [Formula: see text] state in the limit ΔT ≫ λSOC realized in Ag3LiRh2O6, different from the conventional [Formula: see text] state in the limit λSOC ≫ ΔT realized in Li2RhO3. The change of ground state is followed by a marked change of magnetism from a 6 K spin-glass in Li2RhO3 to a 94 K antiferromagnet in Ag3LiRh2O6.
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Affiliation(s)
- Faranak Bahrami
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Xiaodong Hu
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Yonghua Du
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Oleg I. Lebedev
- Laboratoire CRISMAT, ENSICAEN-CNRS UMR6508, 14050 Caen, France
| | - Chennan Wang
- Laboratory for Muon Spin Spectroscopy (LMU), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Hubertus Luetkens
- Laboratory for Muon Spin Spectroscopy (LMU), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Gilberto Fabbris
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Michael J. Graf
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Daniel Haskel
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Ying Ran
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Fazel Tafti
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
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5
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Jo MK, Heo H, Lee JH, Choi S, Kim A, Jeong HB, Jeong HY, Yuk JM, Eom D, Jahng J, Lee ES, Jung IY, Cho SR, Kim J, Cho S, Kang K, Song S. Enhancement of Photoresponse on Narrow-Bandgap Mott Insulator α-RuCl 3 via Intercalation. ACS Nano 2021; 15:18113-18124. [PMID: 34734700 DOI: 10.1021/acsnano.1c06752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Charge doping to Mott insulators is critical to realize high-temperature superconductivity, quantum spin liquid state, and Majorana fermion, which would contribute to quantum computation. Mott insulators also have a great potential for optoelectronic applications; however, they showed insufficient photoresponse in previous reports. To enhance the photoresponse of Mott insulators, charge doping is a promising strategy since it leads to effective modification of electronic structure near the Fermi level. Intercalation, which is the ion insertion into the van der Waals gap of layered materials, is an effective charge-doping method without defect generation. Herein, we showed significant enhancement of optoelectronic properties of a layered Mott insulator, α-RuCl3, through electron doping by organic cation intercalation. The electron-doping results in substantial electronic structure change, leading to the bandgap shrinkage from 1.2 eV to 0.7 eV. Due to localized excessive electrons in RuCl3, distinct density of states is generated in the valence band, leading to the optical absorption change rather than metallic transition even in substantial doping concentration. The stable near-infrared photodetector using electronic modulated RuCl3 showed 50 times higher photoresponsivity and 3 times faster response time compared to those of pristine RuCl3, which contributes to overcoming the disadvantage of a Mott insulator as a promising optoelectronic device and expanding the material libraries.
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Affiliation(s)
- Min-Kyung Jo
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Hoseok Heo
- Inorganic Material Lab., Samsung Advanced Institute of Technology (SAIT), Suwon 16678, Korea
| | - Jung-Hoon Lee
- Computational Science Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Seungwook Choi
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Ansoon Kim
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Han Beom Jeong
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Hu Young Jeong
- UNIST Central Research Facilities (UCRF) and Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
| | - Jong Min Yuk
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Daejin Eom
- Atom-scale Measurement Team, Advanced Instrumentation Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Junghoon Jahng
- Hyperspectral Nano-imaging Lab, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Eun Seong Lee
- Hyperspectral Nano-imaging Lab, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - In-Young Jung
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Seong Rae Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jeongtae Kim
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Seorin Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Kibum Kang
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seungwoo Song
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
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6
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Kim C, Kim HS, Park JG. Spin-orbital entangled state and realization of Kitaev physics in 3 dcobalt compounds: a progress report. J Phys Condens Matter 2021; 34:023001. [PMID: 34614480 DOI: 10.1088/1361-648x/ac2d5d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 10/06/2021] [Indexed: 06/13/2023]
Abstract
The realization of Kitaev's honeycomb magnetic model in real materials has become one of the most pursued topics in condensed matter physics and materials science. If found, it is expected to host exotic quantum phases of matter and offers potential realizations of fault-tolerant quantum computations. Over the past years, much effort has been made on 4d- or 5d-heavy transition metal compounds because of their intrinsic strong spin-orbit coupling. But more recently, there have been growing shreds of evidence that the Kitaev model could also be realized in 3d-transition metal systems with much weaker spin-orbit coupling. This review intends to serve as a guide to this fast-developing field focusing on systems withd7transition metal occupation. It overviews the current theoretical and experimental progress on realizing the Kitaev model in those systems. We examine the recent experimental observations of candidate materials with Co2+ions: e.g., CoPS3, Na3Co2SbO6, and Na2Co2TeO6, followed by a brief review of theoretical backgrounds. We conclude this article by comparing experimental observations with density functional theory calculations. We stress the importance of inter-t2ghopping channels and Hund's coupling in the realization of Kitaev interactions in Co-based compounds, which has been overlooked in previous studies. This review suggests future directions in the search for Kitaev physics in 3dcobalt compounds and beyond.
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Affiliation(s)
- Chaebin Kim
- Center for Quantum Materials, Seoul National University, Seoul 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
| | - Heung-Sik Kim
- Department of Physics and Institute for Accelerator Science, Kangwon National University, Chuncheon 24311, Republic of Korea
| | - Je-Geun Park
- Center for Quantum Materials, Seoul National University, Seoul 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
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7
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Dhingra A, Komesu T, Kumar S, Shimada K, Zhang L, Hong X, Dowben PA. Electronic band structure of iridates. Mater Horiz 2021; 8:2151-2168. [PMID: 34846422 DOI: 10.1039/d1mh00063b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this review, an attempt has been made to compare the electronic structures of various 5d iridates (iridium oxides), with an effort to note the common features and differences. Both experimental studies, especially angle-resolved photoemission spectroscopy (ARPES) results, and first-principles band structure calculations have been discussed. This brings to focus the fact that the electronic structures and magnetic properties of the high-Z 5d transition iridates depend on the intricate interplay of strong electron correlation, strong (relativistic) spin-orbit coupling, lattice distortion, and the dimensionality of the system. For example, in the thin film limit, SrIrO3 exhibits a metal-insulator transition that corresponds to the dimensionality crossover, with the band structure resembling that of bulk Sr2IrO4.
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Affiliation(s)
- Archit Dhingra
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, Theodore Jorgensen Hall, University of Nebraska, 855 N 16th, P. O. Box 880299, Lincoln, Nebraska 68588-0299, USA.
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8
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Suzuki H, Liu H, Bertinshaw J, Ueda K, Kim H, Laha S, Weber D, Yang Z, Wang L, Takahashi H, Fürsich K, Minola M, Lotsch BV, Kim BJ, Yavaş H, Daghofer M, Chaloupka J, Khaliullin G, Gretarsson H, Keimer B. Proximate ferromagnetic state in the Kitaev model material α-RuCl 3. Nat Commun 2021; 12:4512. [PMID: 34301938 PMCID: PMC8302668 DOI: 10.1038/s41467-021-24722-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 07/01/2021] [Indexed: 11/27/2022] Open
Abstract
α-RuCl3 is a major candidate for the realization of the Kitaev quantum spin liquid, but its zigzag antiferromagnetic order at low temperatures indicates deviations from the Kitaev model. We have quantified the spin Hamiltonian of α-RuCl3 by a resonant inelastic x-ray scattering study at the Ru L3 absorption edge. In the paramagnetic state, the quasi-elastic intensity of magnetic excitations has a broad maximum around the zone center without any local maxima at the zigzag magnetic Bragg wavevectors. This finding implies that the zigzag order is fragile and readily destabilized by competing ferromagnetic correlations. The classical ground state of the experimentally determined Hamiltonian is actually ferromagnetic. The zigzag state is stabilized by quantum fluctuations, leaving ferromagnetism – along with the Kitaev spin liquid – as energetically proximate metastable states. The three closely competing states and their collective excitations hold the key to the theoretical understanding of the unusual properties of α-RuCl3 in magnetic fields. RuCl3 has stood out as a prime candidate in the search for quantum spin liquids; however, its antiferromagnetic ordering at low temperature suggests deviations from typical QSL models. Here, using resonant inelastic x-ray scattering, the authors provide a comprehensive determination of the low energy effective Hamiltonian.
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Affiliation(s)
- H Suzuki
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
| | - H Liu
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
| | - J Bertinshaw
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - K Ueda
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Department of Applied Physics, University of Tokyo, Tokyo, Japan
| | - H Kim
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Department of Physics, Pohang University of Science and Technology, Pohang, South Korea.,Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, South Korea
| | - S Laha
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - D Weber
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Z Yang
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - L Wang
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - H Takahashi
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - K Fürsich
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - M Minola
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - B V Lotsch
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Department of Chemistry, University of Munich (LMU), München, Germany
| | - B J Kim
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Department of Physics, Pohang University of Science and Technology, Pohang, South Korea.,Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang, South Korea
| | - H Yavaş
- Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany.,SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - M Daghofer
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, Stuttgart, Germany.,Center for Integrated Quantum Science and Technology, University of Stuttgart, Stuttgart, Germany
| | - J Chaloupka
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic.,Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - G Khaliullin
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
| | - H Gretarsson
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.,Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - B Keimer
- Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
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9
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Paris E, Tseng Y, Pärschke EM, Zhang W, Upton MH, Efimenko A, Rolfs K, McNally DE, Maurel L, Naamneh M, Caputo M, Strocov VN, Wang Z, Casa D, Schneider CW, Pomjakushina E, Wohlfeld K, Radovic M, Schmitt T. Strain engineering of the charge and spin-orbital interactions in Sr 2IrO 4. Proc Natl Acad Sci U S A 2020; 117:24764-70. [PMID: 32958669 DOI: 10.1073/pnas.2012043117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Understanding the relationship between entangled degrees of freedom (DOF) is a central problem in correlated materials and the possibility to influence their balance is promising toward realizing novel functionalities. In Sr2IrO4, the interaction between spin–orbit coupling and electron correlations induces an exotic ground state with magnetotransport properties promising for antiferromagnetic spintronics applications. Moreover, the coupling between orbital and spin DOF renders the magnetic structure sensitive to the Ir–O bond environment. To date, a detailed understanding of the microscopic spin-lattice and electron–phonon interactions is still lacking. Here, we use strain engineering to perturb the local lattice environment and, by tracking the response of the low-energy elementary excitations, we unveil the response of the microscopic spin and charge interactions. In the high spin–orbit-coupled Sr2IrO4, the high sensitivity of the ground state to the details of the local lattice structure shows a large potential for the manipulation of the functional properties by inducing local lattice distortions. We use epitaxial strain to modify the Ir–O bond geometry in Sr2IrO4 and perform momentum-dependent resonant inelastic X-ray scattering (RIXS) at the metal and at the ligand sites to unveil the response of the low-energy elementary excitations. We observe that the pseudospin-wave dispersion for tensile-strained Sr2IrO4 films displays large softening along the [h,0] direction, while along the [h,h] direction it shows hardening. This evolution reveals a renormalization of the magnetic interactions caused by a strain-driven cross-over from anisotropic to isotropic interactions between the magnetic moments. Moreover, we detect dispersive electron–hole pair excitations which shift to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. This behavior shows an intimate coupling between charge excitations and lattice distortions in Sr2IrO4, originating from the modified hopping elements between the t2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr2IrO4 and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin–orbit coupling.
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10
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Lebert BW, Kim S, Bisogni V, Jarrige I, Barbour AM, Kim YJ. Resonant inelastic x-ray scattering study of [Formula: see text]-RuCl 3: a progress report. J Phys Condens Matter 2020; 32:144001. [PMID: 31703223 DOI: 10.1088/1361-648x/ab5595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ru M3-edge resonant inelastic x-ray scattering (RIXS) measurements of [Formula: see text] with 27 meV resolution reveals a spin-orbit exciton without noticeable splitting. We extract values for the spin-orbit coupling constant ([Formula: see text] meV) and trigonal distortion field energy ([Formula: see text] meV) which support the [Formula: see text] nature of [Formula: see text]. We demonstrate the feasibility of M-edge RIXS for 4d systems, which allows ultra high-resolution RIXS of 4d systems until instrumentation for L-edge RIXS improves.
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Affiliation(s)
- Blair W Lebert
- Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada
| | - Subin Kim
- Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada
| | - Valentina Bisogni
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, United States of America
| | - Ignace Jarrige
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, United States of America
| | - Andi M Barbour
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, United States of America
| | - Young-June Kim
- Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada
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11
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Lee I, Utermohlen FG, Weber D, Hwang K, Zhang C, van Tol J, Goldberger JE, Trivedi N, Hammel PC. Fundamental Spin Interactions Underlying the Magnetic Anisotropy in the Kitaev Ferromagnet CrI_{3}. Phys Rev Lett 2020; 124:017201. [PMID: 31976706 DOI: 10.1103/physrevlett.124.017201] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Indexed: 06/10/2023]
Abstract
We lay the foundation for determining the microscopic spin interactions in two-dimensional (2D) ferromagnets by combining angle-dependent ferromagnetic resonance (FMR) experiments on high quality CrI_{3} single crystals with theoretical modeling based on symmetries. We discover that the Kitaev interaction is the strongest in this material with K∼-5.2 meV, 25 times larger than the Heisenberg exchange J∼-0.2 meV, and responsible for opening the ∼5 meV gap at the Dirac points in the spin-wave dispersion. Furthermore, we find that the symmetric off-diagonal anisotropy Γ∼-67.5 μeV, though small, is crucial for opening a ∼0.3 meV gap in the magnon spectrum at the zone center and stabilizing ferromagnetism in the 2D limit. The high resolution of the FMR data further reveals a μeV-scale quadrupolar contribution to the S=3/2 magnetism. Our identification of the underlying exchange anisotropies opens paths toward 2D ferromagnets with higher T_{C} as well as magnetically frustrated quantum spin liquids based on Kitaev physics.
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Affiliation(s)
- Inhee Lee
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Franz G Utermohlen
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Daniel Weber
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Kyusung Hwang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
- School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea
| | - Chi Zhang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Johan van Tol
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
| | - Joshua E Goldberger
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Nandini Trivedi
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - P Chris Hammel
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
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12
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Gompa TP, Ramanathan A, Rice NT, La Pierre HS. The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and Dy. Dalton Trans 2020; 49:15945-15987. [DOI: 10.1039/d0dt01400a] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The thermochemistry, descriptive chemistry, spectroscopy, and physical properties of the tetravalent lanthanides (Pr, Nd, Tb and Dy) in extended phases, gas phase, solution, and as isolable molecular complexes are presented.
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Affiliation(s)
- Thaige P. Gompa
- Department of Chemistry and Biochemistry
- Georgia Institute of Technology
- Atlanta
- USA
| | - Arun Ramanathan
- Department of Chemistry and Biochemistry
- Georgia Institute of Technology
- Atlanta
- USA
| | - Natalie T. Rice
- Department of Chemistry and Biochemistry
- Georgia Institute of Technology
- Atlanta
- USA
| | - Henry S. La Pierre
- Department of Chemistry and Biochemistry
- Georgia Institute of Technology
- Atlanta
- USA
- Nuclear and Radiological Engineering Program
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13
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Abstract
Quantum spin liquids are prime examples of strongly entangled phases of matter with unconventional exotic excitations. Here, strong quantum fluctuations prohibit the freezing of the spin system. On the other hand, frustrated magnets, the proper platforms to search for the quantum spin liquid candidates, still show a magnetic ground state in most of the cases. Pressure is an effective tuning parameter of structural properties and electronic correlations. Nevertheless, the ability to influence the magnetic phases should not be forgotten. We review experimental progress in the field of pressure-tuned magnetic interactions in candidate systems. Elaborating on the possibility of tuned quantum phase transitions, we further show that chemical or external pressure is a suitable parameter in these exotic states of matter.
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14
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Wang Y, Wang R, Kim J, Upton MH, Casa D, Gog T, Cao G, Kotliar G, Dean MPM, Liu X. Direct Detection of Dimer Orbitals in Ba_{5}AlIr_{2}O_{11}. Phys Rev Lett 2019; 122:106401. [PMID: 30932648 DOI: 10.1103/physrevlett.122.106401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Indexed: 06/09/2023]
Abstract
The electronic states of many Mott insulators, including iridates, are often conceptualized in terms of localized atomic states such as the famous "J_{eff}=1/2 state." Although orbital hybridization can strongly modify such states and dramatically change the electronic properties of materials, probing this process is highly challenging. In this Letter, we directly detect and quantify the formation of dimer orbitals in an iridate material Ba_{5}AlIr_{2}O_{11} using resonant inelastic x-ray scattering. Sharp peaks corresponding to the excitations of dimer orbitals are observed and analyzed by a combination of density functional theory calculations and theoretical simulations based on an Ir-Ir cluster model. Such partially delocalized dimer states lead to a redefinition of the angular momentum of the electrons and changes in the magnetic and electronic behaviors of the material. We use this to explain the reduction of the observed magnetic moment with respect to predictions based on atomic states. This study opens new directions to study dimerization in a large family of materials, including solids, heterostructures, molecules, and transient states.
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Affiliation(s)
- Y Wang
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Ruitang Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - M H Upton
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - D Casa
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - T Gog
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - G Cao
- Department of Physics, University of Colorado Boulder, Boulder, Colorado 80309, USA
| | - G Kotliar
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
- Physics and Astronomy Department, Rutgers University, Piscataway, New Jersey 08854, USA
| | - M P M Dean
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - X Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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15
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Yadav R, Eldeeb MS, Ray R, Aswartham S, Sturza MI, Nishimoto S, van den Brink J, Hozoi L. Engineering Kitaev exchange in stacked iridate layers: impact of inter-layer species on in-plane magnetism. Chem Sci 2019; 10:1866-1872. [PMID: 30842855 PMCID: PMC6371754 DOI: 10.1039/c8sc03018a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 12/01/2018] [Indexed: 01/11/2023] Open
Abstract
Electrostatic effects involving the inter-layer species are important: the largest Kitaev interactions comewith a more isotropic distribution of inter-layer cations around a given ligand.
Novel functionalities may be achieved in oxide electronics by appropriate stacking of planar oxide layers of different metallic species, MOp and M′Oq. The simplest mechanism allowing the tailoring of the electronic states and physical properties of such heterostructures is of electrostatic nature—charge imbalance between the M and M′ cations. Here we clarify the effect of interlayer electrostatics on the anisotropic Kitaev exchange in H3LiIr2O6, a recently proposed realization of the Kitaev spin liquid. By quantum chemical calculations, we show that the precise position of H+ cations between magnetically active [LiIr2O6]3– honeycomb-like layers has a strong impact on the magnitude of Kitaev interactions. In particular, it is found that stacking with straight interlayer O–H–O links is detrimental to in-plane Kitaev exchange since coordination by a single H-ion of the O ligand implies an axial Coulomb potential at the O site and unfavorable polarization of the O 2p orbitals mediating the Ir–Ir interactions. Our results therefore provide valuable guidelines for the rational design of Kitaev quantum magnets, indicating unprecedented Kitaev interactions of ≈40 meV if the linear interlayer linkage is removed.
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Affiliation(s)
- Ravi Yadav
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany .
| | - Mohamed S Eldeeb
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany .
| | - Rajyavardhan Ray
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany . .,Dresden Center for Computational Materials Science (DCMS) , TU Dresden , 01062 Dresden , Germany
| | - Saicharan Aswartham
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany .
| | - Mihai I Sturza
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany .
| | - Satoshi Nishimoto
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany . .,Department of Physics , Technical University Dresden , Helmholtzstr. 10 , 01069 Dresden , Germany
| | - Jeroen van den Brink
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany . .,Department of Physics , Technical University Dresden , Helmholtzstr. 10 , 01069 Dresden , Germany
| | - Liviu Hozoi
- Leibniz Institute for Solid State and Materials Research , IFW Dresden , Helmholtzstr. 20 , 01069 Dresden , Germany .
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16
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Revelli A, Moretti Sala M, Monaco G, Becker P, Bohatý L, Hermanns M, Koethe TC, Fröhlich T, Warzanowski P, Lorenz T, Streltsov SV, van Loosdrecht PHM, Khomskii DI, van den Brink J, Grüninger M. Resonant inelastic x-ray incarnation of Young's double-slit experiment. Sci Adv 2019; 5:eaav4020. [PMID: 30746479 PMCID: PMC6357738 DOI: 10.1126/sciadv.aav4020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 12/14/2018] [Indexed: 06/09/2023]
Abstract
Young's archetypal double-slit experiment forms the basis for modern diffraction techniques: The elastic scattering of waves yields an interference pattern that captures the real-space structure. Here, we report on an inelastic incarnation of Young's experiment and demonstrate that resonant inelastic x-ray scattering (RIXS) measures interference patterns, which reveal the symmetry and character of electronic excited states in the same way as elastic scattering does for the ground state. A prototypical example is provided by the quasi-molecular electronic structure of insulating Ba3CeIr2O9 with structural Ir dimers and strong spin-orbit coupling. The double "slits" in this resonant experiment are the highly localized core levels of the two Ir atoms within a dimer. The clear double-slit-type sinusoidal interference patterns that we observe allow us to characterize the electronic excitations, demonstrating the power of RIXS interferometry to unravel the electronic structure of solids containing, e.g., dimers, trimers, ladders, or other superstructures.
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Affiliation(s)
- A. Revelli
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - M. Moretti Sala
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - G. Monaco
- Dipartimento di Fisica, Università di Trento, via Sommarive 14, 38123 Povo (TN), Italy
| | - P. Becker
- Abteilung Kristallographie, Institut für Geologie und Mineralogie, Zülpicher Strasse 49b, D-50674 Köln, Germany
| | - L. Bohatý
- Abteilung Kristallographie, Institut für Geologie und Mineralogie, Zülpicher Strasse 49b, D-50674 Köln, Germany
| | - M. Hermanns
- Institut für Theoretische Physik, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
- Department of Physics, University of Gothenburg, SE-412 96 Gothenburg, Sweden
- Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
| | - T. C. Koethe
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - T. Fröhlich
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - P. Warzanowski
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - T. Lorenz
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - S. V. Streltsov
- M.N. Mikheev Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, 620137 Ekaterinburg, Russia
- Ural Federal University, Mira Street 19, 620002 Ekaterinburg, Russia
| | - P. H. M. van Loosdrecht
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - D. I. Khomskii
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
| | - J. van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - M. Grüninger
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany
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17
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Nemrava S, Link L, Hu Z, Blaschkowski B, Liao SC, Lin HJ, Chen CT, Chan TS, Tjeng LH, Niewa R. Synthesis and Characterization of BaLiRu 5
O 11
, BaCu 1+
x
Ru 5-
x
O 11
, and BaLi 1-
x
Cu
x
+
δ
Ru 5-
δ
O 11
: Crystal Structures and Valence States. Z Anorg Allg Chem 2018. [DOI: 10.1002/zaac.201800058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Sandra Nemrava
- Institut für Anorganische Chemie; Universität Stuttgart; Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Lukas Link
- Institut für Anorganische Chemie; Universität Stuttgart; Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Zhiwei Hu
- Physik korrelierter Materie; Max-Plank-Insitut für Chemische Physik fester Stoffe; Nöthnitzer Straße 40 01187 Dresden Germany
| | - Björn Blaschkowski
- Institut für Anorganische Chemie; Universität Stuttgart; Pfaffenwaldring 55 70569 Stuttgart Germany
| | - Sheng-Chieh Liao
- Physik korrelierter Materie; Max-Plank-Insitut für Chemische Physik fester Stoffe; Nöthnitzer Straße 40 01187 Dresden Germany
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center; 101 Hsin-Ann Road 30077 Hsinchu Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center; 101 Hsin-Ann Road 30077 Hsinchu Taiwan
| | - Ting-Shan Chan
- National Synchrotron Radiation Research Center; 101 Hsin-Ann Road 30077 Hsinchu Taiwan
| | - Liu Hao Tjeng
- Physik korrelierter Materie; Max-Plank-Insitut für Chemische Physik fester Stoffe; Nöthnitzer Straße 40 01187 Dresden Germany
| | - Rainer Niewa
- Institut für Anorganische Chemie; Universität Stuttgart; Pfaffenwaldring 55 70569 Stuttgart Germany
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18
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Li Y, Winter SM, Valentí R. Role of Hydrogen in the Spin-Orbital-Entangled Quantum Liquid Candidate H_{3}LiIr_{2}O_{6}. Phys Rev Lett 2018; 121:247202. [PMID: 30608714 DOI: 10.1103/physrevlett.121.247202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Indexed: 06/09/2023]
Abstract
Motivated by recent reports of H_{3}LiIr_{2}O_{6} as a spin-orbital-entangled quantum liquid, we investigate via a combination of density functional theory and nonperturbative exact diagonalization the microscopic nature of its magnetic interactions. We find that while the interlayer O─H─O bond geometry strongly affects the local magnetic couplings, these bonds are likely to remain symmetrical due to large zero-point fluctuations of the H positions. In this case, the estimated magnetic model lies close to the classical tricritical point between ferromagnetic, zigzag, and incommensurate spiral orders, what may contribute to the lack of magnetic ordering. However, we also find that substitution of H by D (deuterium) as well as disorder-induced inhomogeneities destabilizes the O─H or D─O bonds, modifying strongly the local magnetic couplings. These results suggest that the magnetic response in H_{3}LiIr_{2}O_{6} is likely sensitive to both the stoichiometry and the microstructure of the samples and emphasize the importance of a careful treatment of hydrogen for similar systems.
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Affiliation(s)
- Ying Li
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
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19
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Reschke S, Mayr F, Widmann S, von Nidda HAK, Tsurkan V, Eremin MV, Do SH, Choi KY, Wang Z, Loidl A. Sub-gap optical response in the Kitaev spin-liquid candidate α-RuCl 3. J Phys Condens Matter 2018; 30:475604. [PMID: 30398159 DOI: 10.1088/1361-648x/aae805] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report detailed optical experiments on the layered compound α-RuCl3 focusing on the THz and sub-gap optical response across the structural phase transition from the monoclinic high-temperature to the rhombohedral low-temperature structure, where the stacking sequence of the molecular layers is changed. This type of phase transition is characteristic for a variety of tri-halides crystallizing in a layered honeycomb-type structure and so far is unique, as the low-temperature phase exhibits the higher symmetry. One motivation is to unravel the microscopic nature of THz and spin-orbital excitations via a study of temperature and symmetry-induced changes. The optical studies are complemented by thermal expansion experiments. We document a number of highly unusual findings: A characteristic two-step hysteresis of the structural phase transition, accompanied by a dramatic change of the reflectivity. A complex dielectric loss spectrum in the THz regime, which could indicate remnants of Kitaev physics. Orbital excitations, which cannot be explained based on recent models, and an electronic excitation, which appears in a narrow temperature range just across the structural phase transition. Despite significant symmetry changes across the monoclinic to rhombohedral phase transition and a change of the stacking sequence, phonon eigenfrequencies and the majority of spin-orbital excitations are not strongly influenced. Obviously, the symmetry of a single molecular layer determines the eigenfrequencies of most of these excitations. Only one mode at THz frequencies, which becomes suppressed in the high-temperature monoclinic phase and one phonon mode experience changes in symmetry and stacking. Finally, from this combined terahertz, far- and mid-infrared study we try to shed some light on the so far unsolved low energy (<1 eV) electronic structure of the ruthenium 4d 5 electrons in α-RuCl3.
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Affiliation(s)
- Stephan Reschke
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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20
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Yadav R, Ray R, Eldeeb MS, Nishimoto S, Hozoi L, van den Brink J. Strong Effect of Hydrogen Order on Magnetic Kitaev Interactions in H_{3}LiIr_{2}O_{6}. Phys Rev Lett 2018; 121:197203. [PMID: 30468592 DOI: 10.1103/physrevlett.121.197203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Indexed: 06/09/2023]
Abstract
Very recently a quantum liquid was reported to form in H_{3}LiIr_{2}O_{6}, an iridate proposed to be a close realization of the Kitaev honeycomb model. To test this assertion we perform detailed quantum chemistry calculations to determine the magnetic interactions between Ir moments. We find that weakly bond dependent ferromagnetic Kitaev exchange dominates over other couplings, but still is substantially lower than in Na_{2}IrO_{3}. This reduction is caused by the peculiar position of the interlayer species: removing hydrogen cations next to a Ir_{2}O_{2} plaquette increases the Kitaev exchange by more than a factor of 3 on the corresponding Ir─Ir link. Consequently, any lack of hydrogen order will have a drastic effect on the magnetic interactions and strongly promote spin disordering.
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Affiliation(s)
- Ravi Yadav
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - Rajyavardhan Ray
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
- Dresden Center for Computational Materials Science (DCMS), TU Dresden, 01062 Dresden, Germany
| | - Mohamed S Eldeeb
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - Satoshi Nishimoto
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
- Department of Physics, Technical University Dresden, 01062 Dresden, Germany
| | - Liviu Hozoi
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
- Department of Physics, Technical University Dresden, 01062 Dresden, Germany
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21
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Wang BB, Wang W, Yu SL, Li JX. Dynamics of a single hole in the Heisenberg-Kitaev model: a self-consistent Born approximation study. J Phys Condens Matter 2018; 30:385602. [PMID: 30113017 DOI: 10.1088/1361-648x/aada9c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The magnetic properties of 4d and 5d transition-metal insulating compounds with the honeycomb structure are believed to be described by the Heisenberg-Kitaev model, which contains both the isotropic Heisenberg interaction J and anisotropic Kitaev interaction K. In this paper, we study the single-hole propagation of the t-J-K model in various magnetically ordered phases by the self-consistent Born approximation. We find that there are low-energy coherent quasiparticle (QP) excitations in all of these phases which appear firstly around the K point in the first Brillouin zone (BZ), but the bandwidths of these QPs are very small due to the hole-magnon coupling. Interestingly, in the zigzag phase relevant to recent experiments, though the QP weights are largely suppressed in the physical spectra in the first BZ, we find that they recover in the extended BZs. Moreover, our results reveal that the low-energy QP spectra are reduced with the increase of K.
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Affiliation(s)
- Bin-Bin Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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22
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Yamamoto TD, Taniguchi H, Terasaki I. Dynamical coupling of dilute magnetic impurities with quantum spin liquid state in the S = 3/2 dimer compound Ba 3ZnRu 2O 9. J Phys Condens Matter 2018; 30:355801. [PMID: 30043759 DOI: 10.1088/1361-648x/aad5ac] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We have investigated the dilute magnetic impurity effect on the magnetic properties of a quantum spin liquid candidate Ba3ZnRu2O9 and a spin gapped compound Ba3CaRu2O9. The magnetic ground state of each compound stands against 2% substitution of magnetic impurities for Zn or Ca. We have found that the magnetic response of these impurities, which behave as paramagnetic spins, depends on the host materials and the difference of the two manifests itself in the Weiss temperature, which can hardly be explained by the dilute magnetic impurities alone in the case of Ba3ZnRu2O9. We consider a contribution from the Ru5+ ions which would appear only in the substituted Ba3ZnRu2O9 and discuss a possible physical meaning of the observed Weiss temperature.
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23
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Winter SM, Tsirlin AA, Daghofer M, van den Brink J, Singh Y, Gegenwart P, Valentí R. Models and materials for generalized Kitaev magnetism. J Phys Condens Matter 2017; 29:493002. [PMID: 28914608 DOI: 10.1088/1361-648x/aa8cf5] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The exactly solvable Kitaev model on the honeycomb lattice has recently received enormous attention linked to the hope of achieving novel spin-liquid states with fractionalized Majorana-like excitations. In this review, we analyze the mechanism proposed by Jackeli and Khaliullin to identify Kitaev materials based on spin-orbital dependent bond interactions and provide a comprehensive overview of its implications in real materials. We set the focus on experimental results and current theoretical understanding of planar honeycomb systems (Na2IrO3, α-Li2IrO3, and α-RuCl3), three-dimensional Kitaev materials (β- and γ-Li2IrO3), and other potential candidates, completing the review with the list of open questions awaiting new insights.
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Affiliation(s)
- Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
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24
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Zheng J, Ran K, Li T, Wang J, Wang P, Liu B, Liu ZX, Normand B, Wen J, Yu W. Gapless Spin Excitations in the Field-Induced Quantum Spin Liquid Phase of α-RuCl_{3}. Phys Rev Lett 2017; 119:227208. [PMID: 29286810 DOI: 10.1103/physrevlett.119.227208] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Indexed: 06/07/2023]
Abstract
α-RuCl_{3} is a leading candidate material for the observation of physics related to the Kitaev quantum spin liquid (QSL). By combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, we demonstrate that α-RuCl_{3} undergoes a quantum phase transition to a QSL in a magnetic field of 7.5 T applied in the ab plane. We show further that this high-field QSL phase has gapless spin excitations over a field range up to 16 T. This highly unconventional result, unknown in either Heisenberg or Kitaev magnets, offers insight essential to establishing the physics of α-RuCl_{3}.
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Affiliation(s)
- Jiacheng Zheng
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
- Department of Physics, Beijing Jiaotong University, Beijing 100044, China
| | - Kejing Ran
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Tianrun Li
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Jinghui Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Pengshuai Wang
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - Bin Liu
- Department of Physics, Beijing Jiaotong University, Beijing 100044, China
| | - Zheng-Xin Liu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
| | - B Normand
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Jinsheng Wen
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Innovative Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Weiqiang Yu
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
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25
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Gallo E, Gorelov E, Guda AA, Bugaev AL, Bonino F, Borfecchia E, Ricchiardi G, Gianolio D, Chavan S, Lamberti C. Effect of Molecular Guest Binding on the d–d Transitions of Ni2+ of CPO-27-Ni: A Combined UV–Vis, Resonant-Valence-to-Core X-ray Emission Spectroscopy, and Theoretical Study. Inorg Chem 2017; 56:14408-14425. [DOI: 10.1021/acs.inorgchem.7b01471] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Erik Gallo
- NIS and INSTM Reference
Center, Department of Chemistry, University of Turin, Via Quarello
15, I-10135 Torino, Italy
- European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, BP 220, 38043, Grenoble Cedex
9, France
| | - Evgeny Gorelov
- European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
| | - Alexander A. Guda
- International Research Center “Smart Materials”, Southern Federal University, Zorge Street 5, 344090 Rostov-on-Don, Russia
| | - Aram L. Bugaev
- NIS and INSTM Reference
Center, Department of Chemistry, University of Turin, Via Quarello
15, I-10135 Torino, Italy
- International Research Center “Smart Materials”, Southern Federal University, Zorge Street 5, 344090 Rostov-on-Don, Russia
| | - Francesca Bonino
- NIS and INSTM Reference
Center, Department of Chemistry, University of Turin, Via Quarello
15, I-10135 Torino, Italy
| | - Elisa Borfecchia
- NIS and INSTM Reference
Center, Department of Chemistry, University of Turin, Via Quarello
15, I-10135 Torino, Italy
| | - Gabriele Ricchiardi
- NIS and INSTM Reference
Center, Department of Chemistry, University of Turin, Via Quarello
15, I-10135 Torino, Italy
| | - Diego Gianolio
- Harwell
Science and Innovation Campus, Diamond Light Source Ltd., OX11 0DE Didcot, United Kingdom
| | - Sachin Chavan
- Department of
Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
| | - Carlo Lamberti
- International Research Center “Smart Materials”, Southern Federal University, Zorge Street 5, 344090 Rostov-on-Don, Russia
- CrisDi and INSTM Reference Center, Department of Chemistry, University of Turin, Via P. Giuria 7, I-10125 Torino, Italy
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26
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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. J Phys Condens Matter 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] [What about the content of this article? (0)] [Affiliation(s)] [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.
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Affiliation(s)
- C Martins
- Laboratoire de Chimie et Physique Quantiques, UMR 5626, Université Paul Sabatier, 118 route de Narbonne, 31400 Toulouse, France
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Ran K, Wang J, Wang W, Dong ZY, Ren X, Bao S, Li S, Ma Z, Gan Y, Zhang Y, Park JT, Deng G, Danilkin S, Yu SL, Li JX, Wen J. Spin-Wave Excitations Evidencing the Kitaev Interaction in Single Crystalline α-RuCl_{3}. Phys Rev Lett 2017; 118:107203. [PMID: 28339266 DOI: 10.1103/physrevlett.118.107203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Indexed: 06/06/2023]
Abstract
Kitaev interactions underlying a quantum spin liquid have long been sought, but experimental data from which their strengths can be determined directly, are still lacking. Here, by carrying out inelastic neutron scattering measurements on high-quality single crystals of α-RuCl_{3}, we observe spin-wave spectra with a gap of ∼2 meV around the M point of the two-dimensional Brillouin zone. We derive an effective-spin model in the strong-coupling limit based on energy bands obtained from first-principles calculations, and find that the anisotropic Kitaev interaction K term and the isotropic antiferromagnetic off-diagonal exchange interaction Γ term are significantly larger than the Heisenberg exchange coupling J term. Our experimental data can be well fit using an effective-spin model with K=-6.8 meV and Γ=9.5 meV. These results demonstrate explicitly that Kitaev physics is realized in real materials.
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Affiliation(s)
- Kejing Ran
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Jinghui Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Wei Wang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Zhao-Yang Dong
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Xiao Ren
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Song Bao
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Shichao Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Zhen Ma
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Yuan Gan
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - Youtian Zhang
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
| | - J T Park
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Garching D-85747, Germany
| | - Guochu Deng
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, New South Wale 2234, Australia
| | - S Danilkin
- Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, New South Wale 2234, Australia
| | - Shun-Li Yu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jian-Xin Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jinsheng Wen
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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28
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Kim BH, Shirakawa T, Yunoki S. From a Quasimolecular Band Insulator to a Relativistic Mott Insulator in t_{2g}^{5} Systems with a Honeycomb Lattice Structure. Phys Rev Lett 2016; 117:187201. [PMID: 27835008 DOI: 10.1103/physrevlett.117.187201] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Indexed: 06/06/2023]
Abstract
The t_{2g} orbitals of an edge-shared transition-metal oxide with a honeycomb lattice structure form dispersionless electronic bands when only hopping mediated by the edge-sharing oxygens is accessible. This is due to the formation of isolated quasimolecular orbitals (QMOs) in each hexagon, introduced recently by Mazin et al. [Phys. Rev. Lett. 109, 197201 (2012)], which stabilizes a band insulating phase for t_{2g}^{5} systems. However, with the help of the exact diagonalization method to treat the electron kinetics and correlations on an equal footing, we find that the QMOs are fragile against not only the spin-orbit coupling (SOC) but also the Coulomb repulsion. We show that the electronic phase of t_{2g}^{5} systems can vary from a quasimolecular band insulator to a relativistic J_{eff}=1/2 Mott insulator with increasing the SOC as well as the Coulomb repulsion. The different electronic phases manifest themselves in electronic excitations observed in optical conductivity and resonant inelastic x-ray scattering. Based on our calculations, we assert that the currently known Ru^{3+} and Ir^{4+} based honeycomb systems are far from the quasimolecular band insulator but rather the relativistic Mott insulator.
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Affiliation(s)
- Beom Hyun Kim
- Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
- Interdisciplinary Theoretical Science (iTHES) Research Group, RIKEN, Wako, Saitama 351-0198, Japan
| | - Tomonori Shirakawa
- Computational Quantum Matter Research Team, RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Seiji Yunoki
- Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
- Interdisciplinary Theoretical Science (iTHES) Research Group, RIKEN, Wako, Saitama 351-0198, Japan
- Computational Quantum Matter Research Team, RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Computational Materials Science Research Team, RIKEN Advanced Institute for Computational Science (AICS), Kobe, Hyogo 650-0047, Japan
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Gordon EE, Xiang H, Köhler J, Whangbo MH. Spin orientations of the spin-half Ir(4+) ions in Sr3NiIrO6, Sr2IrO4, and Na2IrO3: Density functional, perturbation theory, and Madelung potential analyses. J Chem Phys 2016; 144:114706. [PMID: 27004892 DOI: 10.1063/1.4943889] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The spins of the low-spin Ir(4+) (S = 1/2, d(5)) ions at the octahedral sites of the oxides Sr3NiIrO6, Sr2IrO4, and Na2IrO3 exhibit preferred orientations with respect to their IrO6 octahedra. We evaluated the magnetic anisotropies of these S = 1/2 ions on the basis of density functional theory (DFT) calculations including spin-orbit coupling (SOC), and probed their origin by performing perturbation theory analyses with SOC as perturbation within the LS coupling scheme. The observed spin orientations of Sr3NiIrO6 and Sr2IrO4 are correctly predicted by DFT calculations, and are accounted for by the perturbation theory analysis. As for the spin orientation of Na2IrO3, both experimental studies and DFT calculations have not been unequivocal. Our analysis reveals that the Ir(4+) spin orientation of Na2IrO3 should have nonzero components along the c- and a-axis directions. The spin orientations determined by DFT calculations are sensitive to the accuracy of the crystal structures employed, which is explained by perturbation theory analyses when interactions between adjacent Ir(4+) ions are taken into consideration. There are indications implying that the 5d electrons of Na2IrO3 are less strongly localized compared with those of Sr3NiIrO6 and Sr2IrO4. This implication was confirmed by showing that the Madelung potentials of the Ir(4+) ions are less negative in Na2IrO3 than in Sr3NiIrO6 and Sr2IrO4. Most transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC induces interactions among their crystal-field split d-states, and the associated mixing of the states modifies only the orbital parts of the states. This finding cannot be mimicked by a spin Hamiltonian because this model Hamiltonian lacks the orbital degree of freedom, thereby leading to the spin-half syndrome. The spin-orbital entanglement for the 5d spin-half ions Ir(4+) is not as strong as has been assumed.
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Affiliation(s)
- Elijah E Gordon
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA
| | - Hongjun Xiang
- Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, Collaborative Innovation Center of Advanced Microstructures, and Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
| | - Jürgen Köhler
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
| | - Myung-Hwan Whangbo
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA
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31
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Katukuri VM, Yadav R, Hozoi L, Nishimoto S, van den Brink J. The vicinity of hyper-honeycomb β-Li2IrO3 to a three-dimensional Kitaev spin liquid state. Sci Rep 2016; 6:29585. [PMID: 27404112 DOI: 10.1038/srep29585] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 06/22/2016] [Indexed: 01/23/2023] Open
Abstract
Due to the combination of a substantial spin-orbit coupling and correlation effects, iridium oxides hold a prominent place in the search for novel quantum states of matter, including, e.g., Kitaev spin liquids and topological Weyl states. We establish the promise of the very recently synthesized hyper-honeycomb iridate β-Li2IrO3 in this regard. A detailed theoretical analysis reveals the presence of large ferromagnetic first-neighbor Kitaev interactions, while a second-neighbor antiferromagnetic Heisenberg exchange drives the ground state from ferro to zigzag order via a three-dimensional Kitaev spin liquid and an incommensurate phase. Experiment puts the system in the latter regime but the Kitaev spin liquid is very close and reachable by a slight modification of the ratio between the second- and first-neighbor couplings, for instance via strain.
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Lv X, Xu Z, Li J, Chen J, Liu Q. Insights into stability, electronic properties, defect properties and Li ions migration of Na, Mg and Al-doped LiVPO4F for cathode materials of lithium ion batteries: A first-principles investigation. J SOLID STATE CHEM 2016. [DOI: 10.1016/j.jssc.2016.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Calder S, Vale JG, Bogdanov NA, Liu X, Donnerer C, Upton MH, Casa D, Said AH, Lumsden MD, Zhao Z, Yan JQ, Mandrus D, Nishimoto S, van den Brink J, Hill JP, McMorrow DF, Christianson AD. Spin-orbit-driven magnetic structure and excitation in the 5d pyrochlore Cd2Os2O7. Nat Commun 2016; 7:11651. [PMID: 27273216 DOI: 10.1038/ncomms11651] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 04/18/2016] [Indexed: 11/09/2022] Open
Abstract
Much consideration has been given to the role of spin-orbit coupling (SOC) in 5d oxides, particularly on the formation of novel electronic states and manifested metal-insulator transitions (MITs). SOC plays a dominant role in 5d5 iridates (Ir4+), undergoing MITs both concurrent (pyrochlores) and separated (perovskites) from the onset of magnetic order. However, the role of SOC for other 5d configurations is less clear. For example, 5d3 (Os5+) systems are expected to have an orbital singlet with reduced effective SOC. The pyrochlore Cd2Os2O7 nonetheless exhibits a MIT entwined with magnetic order phenomenologically similar to pyrochlore iridates. Here, we resolve the magnetic structure in Cd2Os2O7 with neutron diffraction and then via resonant inelastic X-ray scattering determine the salient electronic and magnetic energy scales controlling the MIT. In particular, SOC plays a subtle role in creating the electronic ground state but drives the magnetic order and emergence of a multiple spin-flip magnetic excitation. Strong electronic correlations in 5d materials such as osmates may combine with spin-orbit coupling to yield novel order. Here, the authors demonstrate how spin-orbit coupling in pyrochlore Cd2Os2O7 generates magnetic order and excitations associated with a magnetic metal-insulator transition.
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Ding Y, Yang L, Chen CC, Kim HS, Han MJ, Luo W, Feng Z, Upton M, Casa D, Kim J, Gog T, Zeng Z, Cao G, Mao HK, van Veenendaal M. Pressure-Induced Confined Metal from the Mott Insulator Sr_{3}Ir_{2}O_{7}. Phys Rev Lett 2016; 116:216402. [PMID: 27284666 DOI: 10.1103/physrevlett.116.216402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Indexed: 06/06/2023]
Abstract
The spin-orbit Mott insulator Sr_{3}Ir_{2}O_{7} provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr_{3}Ir_{2}O_{7} up to 63-65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the ab plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials.
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Affiliation(s)
- Yang Ding
- Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, China
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
- HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA
| | - Liuxiang Yang
- Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, China
- HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA
| | - Cheng-Chien Chen
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | - Heung-Sik Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
| | - Myung Joon Han
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea
| | - Wei Luo
- Condensed Matter Theory Group, Department of Physics, Box 530, SE-751 21 Uppsala, Sweden
| | - Zhenxing Feng
- Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Mary Upton
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Diego Casa
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Thomas Gog
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Zhidan Zeng
- Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, China
- HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA
| | - Gang Cao
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Ho-Kwang Mao
- Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, China
- HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA
| | - Michel van Veenendaal
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Physics, Northern Illinois University, De Kalb, Illinois 60115, USA
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35
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Plotnikova EM, Daghofer M, van den Brink J, Wohlfeld K. Jahn-Teller Effect in Systems with Strong On-Site Spin-Orbit Coupling. Phys Rev Lett 2016; 116:106401. [PMID: 27015495 DOI: 10.1103/physrevlett.116.106401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Indexed: 06/05/2023]
Abstract
When strong spin-orbit coupling removes orbital degeneracy, it would at the same time appear to render the Jahn-Teller mechanism ineffective. We discuss such a situation, the t_{2g} manifold of iridates, and show that, while the Jahn-Teller effect does indeed not affect the j_{eff}=1/2 antiferromagnetically ordered ground state, it leads to distinctive signatures in the j_{eff}=3/2 spin-orbit exciton. It allows for a hopping of the spin-orbit exciton between the nearest-neighbor sites without producing defects in the j_{eff}=1/2 antiferromagnet. This arises because the lattice-driven Jahn-Teller mechanism only couples to the orbital degree of freedom but is not sensitive to the phase of the wave function that defines isospin j_{z}. This contrasts sharply with purely electronic propagation, which conserves isospin, and the presence of Jahn-Teller coupling can explain some of the peculiar features of measured resonant inelastic x-ray scattering spectra of Sr_{2}IrO_{4}.
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Affiliation(s)
- Ekaterina M Plotnikova
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - Maria Daghofer
- Institute for Functional Materials and Quantum Technologies, University of Stuttgart, Pfaffenwaldring 57 D-70550 Stuttgart, Germany
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
- Institute for Theoretical Physics, TU Dresden, 01069 Dresden, Germany
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Krzysztof Wohlfeld
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, PL-02093 Warsaw, Poland
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Igarashi JI, Nagao T. Collective excitations in Na2IrO3. J Phys Condens Matter 2016; 28:026006. [PMID: 26683496 DOI: 10.1088/0953-8984/28/2/026006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We study the collective excitations of Na2IrO3 in an itinerant electron approach. We consider a multi-orbital tight-binding model with the electron transfer between the Ir 5d states mediated via oxygen 2p states and the direct d-d transfer on a honeycomb lattice. The one electron energy as well as the ground state energy are investigated within the Hartree-Fock approximation. When the direct d-d transfer is weak, we obtain nearly flat energy bands due to the formation of quasimolecular orbitals, and the ground state exhibits the zigzag spin order. The evaluation of the density-density correlation function within the random phase approximation shows that the collective excitations emerge as bound states. For an appropriate value of the direct d-d transfer, some of them are concentrated in the energy region ω<50 meV(magnetic excitations) while the others lie in the energy region ω>350 meV (excitonic excitations). This behaviour is consistent with the resonant inelastic x-ray scattering spectra. We also show that the larger values of the direct d-d transfer are unfavourable in order to explain the observed aspects of Na2IrO3 such as the ordering pattern of the ground state and the excitation spectrum. These findings may indicate that the direct d-d transfer is suppressed by the structural distortions in the view of excitation spectroscopy, as having been pointed out in the ab initio calculation.
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Affiliation(s)
- Jun-Ichi Igarashi
- Faculty of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
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37
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Affiliation(s)
- Benjamin A. Trump
- Department of Chemistry, ‡Institute for Quantum
Matter, §Department of Physics and Astronomy, and ∥Department of Material Science, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jake A. Tutmaher
- Department of Chemistry, ‡Institute for Quantum
Matter, §Department of Physics and Astronomy, and ∥Department of Material Science, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Tyrel M. McQueen
- Department of Chemistry, ‡Institute for Quantum
Matter, §Department of Physics and Astronomy, and ∥Department of Material Science, Johns Hopkins University, Baltimore, Maryland 21218, United States
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38
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Hermanns M, Trebst S, Rosch A. Spin-Peierls Instability of Three-Dimensional Spin Liquids with Majorana Fermi Surfaces. Phys Rev Lett 2015; 115:177205. [PMID: 26551141 DOI: 10.1103/physrevlett.115.177205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Indexed: 06/05/2023]
Abstract
Three-dimensional (3D) variants of the Kitaev model can harbor gapless spin liquids with a Majorana Fermi surface on certain tricoordinated lattice structures such as the recently introduced hyperoctagon lattice. Here, we investigate Fermi surface instabilities arising from additional spin exchange terms (such as a Heisenberg coupling) which introduce interactions between the emergent Majorana fermion degrees of freedom. We show that independent of the sign and structure of the interactions, the Majorana surface is always unstable. Generically, the system spontaneously doubles its unit cell at exponentially small temperatures and forms a spin liquid with line nodes. Depending on the microscopics, further symmetries of the system can be broken at this transition. These spin-Peierls instabilities of a 3D spin liquid are closely related to BCS instabilities of fermions.
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Affiliation(s)
- Maria Hermanns
- Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany
| | - Simon Trebst
- Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany
| | - Achim Rosch
- Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany
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39
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Katukuri VM, Nishimoto S, Rousochatzakis I, Stoll H, van den Brink J, Hozoi L. Strong magnetic frustration and anti-site disorder causing spin-glass behavior in honeycomb Li2RhO3. Sci Rep 2015; 5:14718. [PMID: 26434954 DOI: 10.1038/srep14718] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/20/2015] [Indexed: 12/04/2022] Open
Abstract
With large spin-orbit coupling, the electron configuration in d-metal oxides is prone to highly anisotropic exchange interactions and exotic magnetic properties. In 5d5 iridates, given the existing variety of crystal structures, the magnetic anisotropy can be tuned from antisymmetric to symmetric Kitaev-type, with interaction strengths that outsize the isotropic terms. By many-body electronic-structure calculations we here address the nature of the magnetic exchange and the intriguing spin-glass behavior of Li2RhO3, a 4d5 honeycomb oxide. For pristine crystals without Rh-Li site inversion, we predict a dimerized ground state as in the isostructural 5d5 iridate Li2IrO3, with triplet spin dimers effectively placed on a frustrated triangular lattice. With Rh-Li anti-site disorder, we explain the observed spin-glass phase as a superposition of different, nearly degenerate symmetry-broken configurations.
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Kim SW, Liu C, Kim HJ, Lee JH, Yao Y, Ho KM, Cho JH. Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3. Phys Rev Lett 2015; 115:096401. [PMID: 26371665 DOI: 10.1103/physrevlett.115.096401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Indexed: 06/05/2023]
Abstract
The insulating ground state of the 5d transition metal oxide CaIrO3 has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir t(2g) states exhibit large splittings and one-dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir^{4+} spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t(2g) states to open an insulating gap. These results indicate that CaIrO_{3} can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal-insulator transition and the paramagnetic to AFM phase transition are concomitant with each other.
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Affiliation(s)
- Sun-Woo Kim
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
| | - Chen Liu
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Hyun-Jung Kim
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
- International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun-Ho Lee
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
- Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722, Korea
| | - Yongxin Yao
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | - Kai-Ming Ho
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
- International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun-Hyung Cho
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
- International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026, China
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Sandilands LJ, Tian Y, Plumb KW, Kim YJ, Burch KS. Scattering continuum and possible fractionalized excitations in α-RuCl(3). Phys Rev Lett 2015; 114:147201. [PMID: 25910156 DOI: 10.1103/physrevlett.114.147201] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Indexed: 06/04/2023]
Abstract
The combination of electronic correlation and spin-orbit coupling is thought to precipitate a variety of highly unusual electronic phases in solids, including topological and quantum spin liquid states. We report a Raman scattering study that provides evidence for unconventional excitations in α-RuCl_{3}, a spin-orbit coupled Mott insulator on the honeycomb lattice. In particular, our measurements reveal unusual magnetic scattering, typified by a broad continuum. The temperature dependence of this continuum is evident over a large scale compared to the magnetic ordering temperature, suggestive of frustrated magnetic interactions. This is confirmed through an analysis of the phonon linewidths, which show a related anomaly due to spin-phonon coupling. These observations are in line with theoretical expectations for the Heisenberg-Kitaev model and suggest that α-RuCl_{3} may be close to a quantum spin liquid ground state.
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Affiliation(s)
- Luke J Sandilands
- Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 1A7, Canada
| | - Yao Tian
- Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 1A7, Canada
| | - Kemp W Plumb
- Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 1A7, Canada
| | - Young-June Kim
- Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario M5S 1A7, Canada
| | - Kenneth S Burch
- Department of Physics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, Massachusetts 02467, USA
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Alpichshev Z, Mahmood F, Cao G, Gedik N. Confinement-deconfinement transition as an indication of spin-liquid-type behavior in Na(2)IrO(3). Phys Rev Lett 2015; 114:017203. [PMID: 25615500 DOI: 10.1103/physrevlett.114.017203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Indexed: 06/04/2023]
Abstract
We use ultrafast optical spectroscopy to observe binding of charged single-particle excitations (SE) in the magnetically frustrated Mott insulator Na(2)IrO(3). Above the antiferromagnetic ordering temperature (T(N)) the system response is due to both Hubbard excitons (HE) and their constituent unpaired SE. The SE response becomes strongly suppressed immediately below T(N). We argue that this increase in binding energy is due to a unique interplay between the frustrated Kitaev and the weak Heisenberg-type ordering term in the Hamiltonian, mediating an effective interaction between the spin-singlet SE. This interaction grows with distance causing the SE to become trapped in the HE, similar to quark confinement inside hadrons. This binding of charged particles, induced by magnetic ordering, is a result of a confinement-deconfinement transition of spin excitations. This observation provides evidence for spin liquid type behavior which is expected in Na(2)IrO(3).
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Affiliation(s)
- Zhanybek Alpichshev
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Fahad Mahmood
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Gang Cao
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Nuh Gedik
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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44
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Abstract
Two new honeycomb Ir5+ iridates are the first examples of a J = 0 state on a honeycomb lattice.
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Affiliation(s)
- David C. Wallace
- Department of Chemistry
- The Johns Hopkins University
- Baltimore
- USA
- Institute for Quantum Matter
| | - Tyrel M. McQueen
- Department of Chemistry
- The Johns Hopkins University
- Baltimore
- USA
- Institute for Quantum Matter
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45
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Abstract
This Progress Report discusses the chemical sensitivity of Kβ valence to core X-ray emission spectroscopy (vtc-XES) and its applications for investigating 3d-transition-metal based materials. Vtc-XES can be used for ligand identification and for the characterization of the valence electronic levels. The technique provides information that is similar to valence band photoemission spectroscopy but the sample environment can be chosen freely and thus allows measurements in presence of gases and liquids and it can be applied for measurements under in situ/operando or extreme conditions. The theoretical basis of the technique is presented using a one-electron approach and the vtc-XES spectral features are interpreted using ground state density functional theory calculations. Some recent results obtained by vtc-XES in various scientific fields are discussed to demonstrate the potential and future applications of this technique. Resonant X-ray emission spectroscopy is briefly introduced with some applications for the study of 3d and 5d-transition-metal based systems.
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Affiliation(s)
- Erik Gallo
- ESRF - The European Synchrotron, 71 Avenue des Martyres, Grenoble, 38000, France
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46
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Cook AM, Paramekanti A. Double perovskite heterostructures: magnetism, Chern bands, and Chern insulators. Phys Rev Lett 2014; 113:077203. [PMID: 25170730 DOI: 10.1103/physrevlett.113.077203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 06/03/2023]
Abstract
Experiments demonstrating the controlled growth of oxide heterostructures have raised the prospect of realizing topologically nontrivial states of correlated electrons in low dimensions. Here, we study heterostructures consisting of {111} bilayers of double perovskites separated by inert band insulators. In bulk, these double perovskites have well-defined local moments interacting with itinerant electrons leading to high temperature ferromagnetism. Incorporating spin-orbit coupling in the two-dimensional honeycomb geometry of a {111} bilayer, we find a rich phase diagram with tunable ferromagnetic order, topological Chern bands, and a C=±2 Chern insulator regime. Our results are of broad relevance to oxide materials such as Sr_{2}FeMoO_{6}, Ba_{2}FeReO_{6}, and Sr_{2}CrWO_{6}.
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Affiliation(s)
- Ashley M Cook
- Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Arun Paramekanti
- Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada and Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
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Lee S, Park J, Kim J, Hong KP, Song Y, Park JG. Experimental percolation studies of two-dimensional honeycomb lattice: Li2Mn1-xTixO3. J Phys Condens Matter 2014; 26:306002. [PMID: 25001600 DOI: 10.1088/0953-8984/26/30/306002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Li2MnO3 with a S = 3/2 two-dimensional Mn honeycomb lattice has a Neel-type antiferromagnetic transition at TN = 36 K with a broad maximum in magnetic susceptibility at TM = 48 K. We have investigated site percolation effects by replacing Mn with nonmagnetic Ti, and completed a full phase diagram of Li2Mn1-xTixO3 solid solution systems to find that antiferromagnetic transition is continuously suppressed without a clear sign of changes in the Neel-type antiferromagnetic structure. The magnetic ordering eventually disappears at a critical concentration of xc = 0.7. This experimental observation is consistent with percolation theories for a honeycomb lattice when one considers up to 3rd nearest-neighbor interactions. This study highlights the importance of interaction beyond nearest neighbors even for the Mn element with relative localized 3d electrons in the honeycomb lattice.
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Affiliation(s)
- Sanghyun Lee
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea. Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-742, Korea. Department of Physics, SungKyunKwan University, Suwon 440-746, Korea
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48
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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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 06/19/2014] [Indexed: 11/09/2022] Open
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Abstract
Using a hybrid density-functional theory (DFT) calculation including spin-orbit coupling (SOC), we predict that the zigzag antiferromagnetic (AFM) ground state of the honeycomb layered compound Na₂IrO₃ opens the observed insulating gap through a long-range magnetic order. We show that the effect of SOC and the correction of self-interaction error inherent in previous local or semilocal DFT calculations play crucial roles in predicting the band gap formation in Na₂IrO₃. It is revealed that the itinerant AFM order with a strong suppression of the Ir magnetic moment is attributed to a considerable hybridization of the Ir 5d orbitals with the O 2p orbitals. Thus, our results suggest that the insulating phase of Na₂IrO₃ can be represented as a Slater insulator driven by itinerant magnetism.
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Affiliation(s)
- Hyun-Jung Kim
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
| | - Jun-Ho Lee
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
| | - Jun-Hyung Cho
- Department of Physics and Research Institute for Natural Sciences, Hanyang University, 17 Haengdang-Dong, Seongdong-Ku, Seoul 133-791, Korea
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50
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Sala MM, Ohgushi K, Al-Zein A, Hirata Y, Monaco G, Krisch M. CaIrO3: a spin-orbit Mott insulator beyond the j(eff) ground state. Phys Rev Lett 2014; 112:176402. [PMID: 24836260 DOI: 10.1103/physrevlett.112.176402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Indexed: 06/03/2023]
Abstract
In CaIrO3, electronic correlation, spin-orbit coupling, and tetragonal crystal field splitting are predicted to be of comparable strength. However, the nature of its ground state is still an object of debate, with contradictory experimental and theoretical results. We probe the ground state of CaIrO3 and assess the effective tetragonal crystal field splitting and spin-orbit coupling at play in this system by means of resonant inelastic x-ray scattering. We conclude that insulating CaIrO3 is not a j(eff) = 1/2 iridate and discuss the consequences of our finding to the interpretation of previous experiments. In particular, we clarify how the Mott insulating state in iridates can be readily extended beyond the j(eff) = 1/2 ground state.
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Affiliation(s)
- M Moretti Sala
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - K Ohgushi
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - A Al-Zein
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - Y Hirata
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - G Monaco
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France and Dipartimento di Fisica, Università di Trento, via Sommarive 14, 38123 Povo (TN), Italy
| | - M Krisch
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
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