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Abstract
Excitonic insulators are usually considered to form via the condensation of a soft charge mode of bound electron-hole pairs. This, however, presumes that the soft exciton is of spin-singlet character. Early theoretical considerations have also predicted a very distinct scenario, in which the condensation of magnetic excitons results in an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements of Sr3Ir2O7. By isolating the longitudinal component of the spectra, we identify a magnetic mode that is well-defined at the magnetic and structural Brillouin zone centers, but which merges with the electronic continuum in between these high symmetry points and which decays upon heating concurrent with a decrease in the material’s resistivity. We show that a bilayer Hubbard model, in which electron-hole pairs are bound by exchange interactions, consistently explains all the electronic and magnetic properties of Sr3Ir2O7 indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulator phase. Antiferromagnetic excitonic insulators are a distinct form of excitonic insulator, in which electrons and holes are bound by magnetic exchange rather than Coulomb attraction. Here, Mazzone et al. show, using X-ray scattering, that Sr3Ir2O7 realizes this particular state.
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Zhao H, Porter Z, Chen X, Wilson SD, Wang Z, Zeljkovic I. Imaging antiferromagnetic domain fluctuations and the effect of atomic scale disorder in a doped spin-orbit Mott insulator. SCIENCE ADVANCES 2021; 7:eabi6468. [PMID: 34757784 PMCID: PMC8580306 DOI: 10.1126/sciadv.abi6468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 09/20/2021] [Indexed: 06/13/2023]
Abstract
Correlated oxides can exhibit complex magnetic patterns. Understanding how magnetic domains form in the presence of disorder and their robustness to temperature variations has been of particular interest, but atomic scale insight has been limited. We use spin-polarized scanning tunneling microscopy to image the evolution of spin-resolved modulations originating from antiferromagnetic (AF) ordering in a spin-orbit Mott insulator perovskite iridate Sr3Ir2O7 as a function of chemical composition and temperature. We find that replacing only several percent of lanthanum for strontium leaves behind nanometer-scale AF puddles clustering away from lanthanum substitutions preferentially located in the middle strontium oxide layer. Thermal erasure and reentry into the low-temperature ground state leads to a spatial reorganization of the AF puddles, which nevertheless maintain scale-invariant fractal geometry in each configuration. Our experiments reveal multiple stable AF configurations at low temperature and shed light onto spatial fluctuations of the AF order around atomic scale disorder in electron-doped Sr3Ir2O7.
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Affiliation(s)
- He Zhao
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Zach Porter
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Xiang Chen
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Stephen D. Wilson
- Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
| | - Ilija Zeljkovic
- Department of Physics, Boston College, Chestnut Hill, MA 02467, USA
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Evidence for one-dimensional chiral edge states in a magnetic Weyl semimetal Co 3Sn 2S 2. Nat Commun 2021; 12:4269. [PMID: 34257284 PMCID: PMC8277809 DOI: 10.1038/s41467-021-24561-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 06/20/2021] [Indexed: 11/23/2022] Open
Abstract
The physical realization of Chern insulators is of fundamental and practical interest, as they are predicted to host the quantum anomalous Hall (QAH) effect and topologically protected chiral edge states which can carry dissipationless current. Current realizations of the QAH state often require complex heterostructures and sub-Kelvin temperatures, making the discovery of intrinsic, high temperature QAH systems of significant interest. In this work we show that time-reversal symmetry breaking Weyl semimetals, being essentially stacks of Chern insulators with inter-layer coupling, may provide a new platform for the higher temperature realization of robust chiral edge states. We present combined scanning tunneling spectroscopy and theoretical investigations of the magnetic Weyl semimetal, Co3Sn2S2. Using modeling and numerical simulations we find that depending on the strength of the interlayer coupling, chiral edge states can be localized on partially exposed kagome planes on the surfaces of a Weyl semimetal. Correspondingly, our dI/dV maps on the kagome Co3Sn terraces show topological states confined to the edges which display linear dispersion. This work provides a new paradigm for realizing chiral edge modes and provides a pathway for the realization of higher temperature QAH effect in magnetic Weyl systems in the two-dimensional limit. Magnetic Weyl semimetals in the 2D limit may behave like 2D Chern insulators and host the quantum anomalous Hall effect at high temperatures. Here, the authors report the observation of linearly dispersing topological states confined to the edges of the kagome Co3Sn terraces in the magnetic Weyl system Co3Sn2S2.
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4
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Advanced First-Principle Modeling of Relativistic Ruddlesden—Popper Strontium Iridates. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11062527] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this review, we provide a survey of the application of advanced first-principle methods on the theoretical modeling and understanding of novel electronic, optical, and magnetic properties of the spin-orbit coupled Ruddlesden–Popper series of iridates Srn+1IrnO3n+1 (n = 1, 2, and ∞). After a brief description of the basic aspects of the adopted methods (noncollinear local spin density approximation plus an on-site Coulomb interaction (LSDA+U), constrained random phase approximation (cRPA), GW, and Bethe–Salpeter equation (BSE)), we present and discuss select results. We show that a detailed phase diagrams of the metal–insulator transition and magnetic phase transition can be constructed by inspecting the evolution of electronic and magnetic properties as a function of Hubbard U, spin–orbit coupling (SOC) strength, and dimensionality n, which provide clear evidence for the crucial role played by SOC and U in establishing a relativistic (Dirac) Mott–Hubbard insulating state in Sr2IrO4 and Sr3Ir2O7. To characterize the ground-state phases, we quantify the most relevant energy scales fully ab initio—crystal field energy, Hubbard U, and SOC constant of three compounds—and discuss the quasiparticle band structures in detail by comparing GW and LSDA+U data. We examine the different magnetic ground states of structurally similar n = 1 and n = 2 compounds and clarify that the origin of the in-plane canted antiferromagnetic (AFM) state of Sr2IrO4 arises from competition between isotropic exchange and Dzyaloshinskii–Moriya (DM) interactions whereas the collinear AFM state of Sr3Ir2O7 is due to strong interlayer magnetic coupling. Finally, we report the dimensionality controlled metal–insulator transition across the series by computing their optical transitions and conductivity spectra at the GW+BSE level from the the quasi two-dimensional insulating n = 1 and 2 phases to the three-dimensional metallic n=∞ phase.
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Li S, Drueke E, Porter Z, Jin W, Lu Z, Smirnov D, Merlin R, Wilson SD, Sun K, Zhao L. Symmetry-Resolved Two-Magnon Excitations in a Strong Spin-Orbit-Coupled Bilayer Antiferromagnet. PHYSICAL REVIEW LETTERS 2020; 125:087202. [PMID: 32909791 DOI: 10.1103/physrevlett.125.087202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/29/2020] [Indexed: 06/11/2023]
Abstract
We used a combination of polarized Raman spectroscopy and spin wave calculations to study magnetic excitations in the strong spin-orbit-coupled bilayer perovskite antiferromagnet Sr_{3}Ir_{2}O_{7}. We observed two broad Raman features at ∼800 and ∼1400 cm^{-1} arising from magnetic excitations. Unconventionally, the ∼800 cm^{-1} feature is fully symmetric (A_{1g}) with respect to the underlying tetragonal (D_{4h}) crystal lattice which, together with its broad line shape, definitively rules out the possibility of a single magnon excitation as its origin. In contrast, the ∼1400 cm^{-1} feature shows up in both the A_{1g} and B_{2g} channels. From spin wave and two-magnon scattering cross-section calculations of a tetragonal bilayer antiferromagnet, we identified the ∼800 cm^{-1} (1400 cm^{-1}) feature as two-magnon excitations with pairs of magnons from the zone-center Γ point (zone-boundary van Hove singularity X point). We further found that this zone-center two-magnon scattering is unique to bilayer perovskite magnets which host an optical branch in addition to the acoustic branch, as compared to their single layer counterparts. This zone-center two-magnon mode is distinct in symmetry from the time-reversal symmetry broken "spin wave gap" and "phase mode" proposed to explain the ∼92 meV (742 cm^{-1}) gap in resonant inelastic x-ray spectroscopy magnetic excitation spectra of Sr_{3}Ir_{2}O_{7}.
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Affiliation(s)
- Siwen Li
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Elizabeth Drueke
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Zach Porter
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Wencan Jin
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Zhengguang Lu
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
- Department of Physics, Florida State University, Tallahassee, Florida 32310, USA
| | - Dmitry Smirnov
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
| | - Roberto Merlin
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Stephen D Wilson
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Kai Sun
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Liuyan Zhao
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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6
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Zhong Y, Fan JQ, Wang RF, Wang S, Zhang X, Zhu Y, Dou Z, Yu XQ, Wang Y, Zhang D, Zhu J, Song CL, Ma XC, Xue QK. Direct Visualization of Ambipolar Mott Transition in Cuprate CuO_{2} Planes. PHYSICAL REVIEW LETTERS 2020; 125:077002. [PMID: 32857570 DOI: 10.1103/physrevlett.125.077002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 06/24/2020] [Accepted: 07/16/2020] [Indexed: 06/11/2023]
Abstract
Identifying the essence of doped Mott insulators is one of the major outstanding problems in condensed matter physics and the key to understanding the high-temperature superconductivity in cuprates. We report real space visualization of Mott insulator-metal transition in Sr_{1-x}La_{x}CuO_{2+y} cuprate films that cover both the electron- and hole-doped regimes. Tunneling conductance measurements directly on the copper-oxide (CuO_{2}) planes reveal a systematic shift in the Fermi level, while the fundamental Mott-Hubbard band structure remains unchanged. This is further demonstrated by exploring the atomic-scale electronic response of CuO_{2} to substitutional dopants and intrinsic defects in a sister compound Sr_{0.92}Nd_{0.08}CuO_{2}. The results may be better explained in the framework of self-modulation doping, similar to that in semiconductor heterostructures, and form a basis for developing any microscopic theories for cuprate superconductivity.
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Affiliation(s)
- Yong Zhong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Jia-Qi Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Rui-Feng Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - ShuZe Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xuefeng Zhang
- Institute of Physics, National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Yuying Zhu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ziyuan Dou
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xue-Qing Yu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Yang Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ding Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Jing Zhu
- Institute of Physics, National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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7
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Vale JG, Boseggia S, Walker HC, Springell RS, Hunter EC, Perry RS, Collins SP, McMorrow DF. Critical fluctuations in the spin-orbit Mott insulator Sr 3Ir 2O 7. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:185803. [PMID: 30721882 DOI: 10.1088/1361-648x/ab0471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
X-ray magnetic critical scattering measurements and specific heat measurements were performed on the perovskite iridate [Formula: see text]. We find that the magnetic interactions close to the Néel temperature [Formula: see text] are three-dimensional. This contrasts with previous studies which suggest two-dimensional behaviour like Sr2IrO4. Violation of the Harris criterion ([Formula: see text]) means that weak disorder becomes relevant. This leads a rounding of the antiferromagnetic phase transition at [Formula: see text], and modifies the critical exponents relative to the clean system. Specifically, we determine that the critical behaviour of [Formula: see text] is representative of the diluted 3D Ising universality class.
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Affiliation(s)
- J G Vale
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London (UCL), Gower Street, London, WC1E 6BT, United Kingdom. Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
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8
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Schmehr JL, Mion TR, Porter Z, Aling M, Cao H, Upton MH, Islam Z, He RH, Sensarma R, Trivedi N, Wilson SD. Overdamped Antiferromagnetic Strange Metal State in Sr_{3}IrRuO_{7}. PHYSICAL REVIEW LETTERS 2019; 122:157201. [PMID: 31050510 DOI: 10.1103/physrevlett.122.157201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 01/24/2019] [Indexed: 06/09/2023]
Abstract
The unconventional electronic ground state of Sr_{3}IrRuO_{7} is explored via resonant x-ray scattering techniques and angle-resolved photoemission measurements. As the Ru content approaches x=0.5 in Sr_{3}(Ir_{1-x}Ru_{x})_{2}O_{7}, intermediate to the J_{eff}=1/2 Mott state in Sr_{3}Ir_{2}O_{7} and the quantum critical metal in Sr_{3}Ru_{2}O_{7}, a thermodynamically distinct metallic state emerges. The electronic structure of this intermediate phase lacks coherent quasiparticles, and charge transport exhibits a linear temperature dependence over a wide range of temperatures. Spin dynamics associated with the long-range antiferromagnetism of this phase show nearly local, overdamped magnetic excitations and an anomalously large energy scale of 200 meV-an energy far in excess of exchange energies present within either the Sr_{3}Ir_{2}O_{7} or Sr_{3}Ru_{2}O_{7} solid-solution end points. Overdamped quasiparticle dynamics driven by strong spin-charge coupling are proposed to explain the incoherent spectral features of the strange metal state in Sr_{3}IrRuO_{7}.
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Affiliation(s)
- Julian L Schmehr
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Thomas R Mion
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Zach Porter
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Michael Aling
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - Huibo Cao
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Mary H Upton
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Zahirul Islam
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Rui-Hua He
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Rajdeep Sensarma
- Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Nandini Trivedi
- Mathematics Department, The Ohio State University, Columbus, Ohio 43210, USA
| | - Stephen D Wilson
- Materials Department, University of California, Santa Barbara, California 93106, USA
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9
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Wang Z, Okada Y, O'Neal J, Zhou W, Walkup D, Dhital C, Hogan T, Clancy P, Kim YJ, Hu YF, Santos LH, Wilson SD, Trivedi N, Madhavan V. Disorder induced power-law gaps in an insulator-metal Mott transition. Proc Natl Acad Sci U S A 2018; 115:11198-11202. [PMID: 30322914 PMCID: PMC6217382 DOI: 10.1073/pnas.1808056115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A correlated material in the vicinity of an insulator-metal transition (IMT) exhibits rich phenomenology and a variety of interesting phases. A common avenue to induce IMTs in Mott insulators is doping, which inevitably leads to disorder. While disorder is well known to create electronic inhomogeneity, recent theoretical studies have indicated that it may play an unexpected and much more profound role in controlling the properties of Mott systems. Theory predicts that disorder might play a role in driving a Mott insulator across an IMT, with the emergent metallic state hosting a power-law suppression of the density of states (with exponent close to 1; V-shaped gap) centered at the Fermi energy. Such V-shaped gaps have been observed in Mott systems, but their origins are as-yet unknown. To investigate this, we use scanning tunneling microscopy and spectroscopy to study isovalent Ru substitutions in Sr3(Ir1-xRux)2O7 (0 ≤ x ≤ 0.5) which drive the system into an antiferromagnetic, metallic state. Our experiments reveal that many core features of the IMT, such as power-law density of states, pinning of the Fermi energy with increasing disorder, and persistence of antiferromagnetism, can be understood as universal features of a disordered Mott system near an IMT and suggest that V-shaped gaps may be an inevitable consequence of disorder in doped Mott insulators.
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Affiliation(s)
- Zhenyu Wang
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801
- Frederick Seitz Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801
| | - Yoshinori Okada
- Quantum Materials Science Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan
| | - Jared O'Neal
- Mathematics Department, The Ohio State University, Columbus, OH 43210
| | - Wenwen Zhou
- Department of Physics, Boston College, Chestnut Hill, MA 02467
| | - Daniel Walkup
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Chetan Dhital
- Department of Physics, Kennesaw State University, Marietta, GA 30060
| | - Tom Hogan
- Materials Department, University of California, Santa Barbara, CA 93106
| | - Patrick Clancy
- Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
| | - Young-June Kim
- Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
| | - Y F Hu
- Canadian Light Source, Saskatoon, SK S7N 2V3, Canada
| | - Luiz H Santos
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801
- Institute for Condensed Matter Theory, University of Illinois Urbana-Champaign, Urbana, IL 61801
| | - Stephen D Wilson
- Materials Department, University of California, Santa Barbara, CA 93106
| | - Nandini Trivedi
- Department of Physics, The Ohio State University, Columbus, Ohio 43210
| | - Vidya Madhavan
- Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801;
- Frederick Seitz Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL 61801
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10
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Chu H, Zhao L, de la Torre A, Hogan T, Wilson SD, Hsieh D. A charge density wave-like instability in a doped spin-orbit-assisted weak Mott insulator. NATURE MATERIALS 2017; 16:200-203. [PMID: 28092687 DOI: 10.1038/nmat4836] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 11/21/2016] [Indexed: 06/06/2023]
Abstract
Layered perovskite iridates realize a rare class of Mott insulators that are predicted to be strongly spin-orbit coupled analogues of the parent state of cuprate high-temperature superconductors. Recent discoveries of pseudogap, magnetic multipolar ordered and possible d-wave superconducting phases in doped Sr2IrO4 have reinforced this analogy among the single layer variants. However, unlike the bilayer cuprates, no electronic instabilities have been reported in the doped bilayer iridate Sr3Ir2O7. Here we show that Sr3Ir2O7 realizes a weak Mott state with no cuprate analogue by using ultrafast time-resolved optical reflectivity to uncover an intimate connection between its insulating gap and antiferromagnetism. However, we detect a subtle charge density wave-like Fermi surface instability in metallic electron doped Sr3Ir2O7 at temperatures (TDW) close to 200 K via the coherent oscillations of its collective modes, which is reminiscent of that observed in cuprates. The absence of any signatures of a new spatial periodicity below TDW from diffraction, scanning tunnelling and photoemission based probes suggests an unconventional and possibly short-ranged nature of this density wave order.
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Affiliation(s)
- H Chu
- Department of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - L Zhao
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - A de la Torre
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - T Hogan
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - S D Wilson
- Materials Department, University of California, Santa Barbara, California 93106, USA
| | - D Hsieh
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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11
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Lu X, McNally DE, Moretti Sala M, Terzic J, Upton MH, Casa D, Ingold G, Cao G, Schmitt T. Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7}. PHYSICAL REVIEW LETTERS 2017; 118:027202. [PMID: 28128620 DOI: 10.1103/physrevlett.118.027202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Indexed: 06/06/2023]
Abstract
We use resonant elastic and inelastic x-ray scattering at the Ir-L_{3} edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} (0≤x≤0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x=0 to 0.05, followed by a transition to two-dimensional short range order between x=0.05 and 0.065. Because of the interactions between the J_{eff}=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the J_{eff}=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.
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Affiliation(s)
- Xingye Lu
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - D E McNally
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Moretti Sala
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - J Terzic
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
- Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, 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
| | - G Ingold
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - G Cao
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
- Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - T Schmitt
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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12
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Sun W, Liu JY, Gong XQ, Zaman WQ, Cao LM, Yang J. OER activity manipulated by IrO 6 coordination geometry: an insight from pyrochlore iridates. Sci Rep 2016; 6:38429. [PMID: 27910932 PMCID: PMC5133550 DOI: 10.1038/srep38429] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/09/2016] [Indexed: 02/03/2023] Open
Abstract
The anodic reaction of oxygen evolution reaction (OER), an important point for electrolysis, however, remains the obstacle due to its complicated reaction at electrochemical interfaces. Iridium oxide (IrO2) is the only currently known 5d transition metal oxide possessing admirable OER activity. Tremendous efforts have been carried out to enhance the activity of iridium oxides. Unfortunately there lies a gap in understanding what factors responsible for the activity in doped IrO2 or the novel crystal structure. Based on two metallic pyrochlores (Bi2Ir2O7 and Pb2Ir2O6.5) and IrO2. It has been found that there exists a strong correlation between the specific OER activity and IrO6 coordination geometry. The more distortion in IrO6 geometry ascends the activity of Ir sites, and generates activity order of Pb-Ir > IrO2 > Bi-Ir. Our characterizations reveal that distorted IrO6 in Pb-Ir induces a disappearance of J = 1/2 subbands in valence band, while Bi-Ir and IrO2 resist this nature probe. The performed DFT calculations indicated the distortion in IrO6 geometry can optimize binding strength between Ir-5d and O-2p due to broader d band width. Based on this insight, enhancement in OER activity is obtained by effects that change IrO6 octahedral geometry through doping or utilizing structural manipulation with nature of distorted octahedral coordination.
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Affiliation(s)
- Wei Sun
- State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Processes, School of Resources and Environmental Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Ji-Yuan Liu
- Key Laboratory for Advanced Materials, Center for Computational Chemistry and Research Institute of Industrial Catalysis, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Xue-Qing Gong
- Key Laboratory for Advanced Materials, Center for Computational Chemistry and Research Institute of Industrial Catalysis, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Waqas-Qamar Zaman
- State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Processes, School of Resources and Environmental Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Li-Mei Cao
- State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Processes, School of Resources and Environmental Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
| | - Ji Yang
- State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Processes, School of Resources and Environmental Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China
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13
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Ahn G, Song SJ, Hogan T, Wilson SD, Moon SJ. Infrared Spectroscopic Evidences of Strong Electronic Correlations in (Sr1-xLax)3Ir2O7. Sci Rep 2016; 6:32632. [PMID: 27599573 PMCID: PMC5013521 DOI: 10.1038/srep32632] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/11/2016] [Indexed: 11/09/2022] Open
Abstract
We report on infrared spectroscopic studies of the electronic response of the (Sr1-xLax)3Ir2O7 system. Our experiments revealed hallmarks of strong electronic correlations in the evolution of the electronic response across the filling-controlled insulator-metal transition. We observed a collapse of the Jeff = 1/2 Mott gap accompanying the transfer of the spectral weight from the high-energy region to the gap region with electron doping. The intraband conductivity at the metallic side of the transition was found to consist of coherent Drude-like and incoherent responses. The sum rule and the extended Drude model analyses further indicated a large mass enhancement. Our results demonstrate a critical role of the electronic correlations in the charge dynamics of the (Sr1-xLax)3Ir2O7 system.
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Affiliation(s)
- Gihyeon Ahn
- Department of Physics, Hanyang University, Seoul 04763, Korea
| | - S. J. Song
- Department of Physics, Hanyang University, Seoul 04763, Korea
| | - T. Hogan
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
- Department of Materials, University of California, Santa Barbara, California 93106, USA
| | - S. D. Wilson
- Department of Materials, University of California, Santa Barbara, California 93106, USA
| | - S. J. Moon
- Department of Physics, Hanyang University, Seoul 04763, Korea
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14
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Nakayama M, Kondo T, Tian Z, Ishikawa JJ, Halim M, Bareille C, Malaeb W, Kuroda K, Tomita T, Ideta S, Tanaka K, Matsunami M, Kimura S, Inami N, Ono K, Kumigashira H, Balents L, Nakatsuji S, Shin S. Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}. PHYSICAL REVIEW LETTERS 2016; 117:056403. [PMID: 27517783 DOI: 10.1103/physrevlett.117.056403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Indexed: 06/06/2023]
Abstract
We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd_{2}Ir_{2}O_{7} through its magnetic metal-insulator transition. Our data reveal that metallic Nd_{2}Ir_{2}O_{7} has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr_{2}Ir_{2}O_{7}. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.
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Affiliation(s)
- M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Z Tian
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - J J Ishikawa
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Halim
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - C Bareille
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - W Malaeb
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Physics Department, Faculty of Science, Beirut Arab University, Beirut 11-5020, Lebanon
| | - K Kuroda
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - T Tomita
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - S Ideta
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - K Tanaka
- UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - M Matsunami
- Toyota Technological Institute, Nagoya 468-8511, Japan
| | - S Kimura
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - N Inami
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Ono
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - L Balents
- Kavli Institute for Theoretical Physics, Santa Barbara, California 93106, USA
| | - S Nakatsuji
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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15
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Direct observation of the Dirac nodes lifting in semimetallic perovskite SrIrO3 thin films. Sci Rep 2016; 6:30309. [PMID: 27457516 PMCID: PMC4960618 DOI: 10.1038/srep30309] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 06/30/2016] [Indexed: 12/01/2022] Open
Abstract
Perovskite SrIrO3 has long been proposed as an exotic semimetal induced by the interplay between the spin-orbit coupling and electron correlations. However, its low-lying electronic structure is still lacking. We synthesize high-quality perovskite SrIrO3 (100) films by means of oxide molecular beam epitaxy, and then systemically investigate their low energy electronic structure using in-situ angle-resolved photoemission spectroscopy. We find that the hole-like bands around R and the electron-like bands around U(T) intersect the Fermi level simultaneously, providing the direct evidence of the semimetallic ground state in this compound. Comparing with the density functional theory, we discover that the bandwidth of states near Fermi level is extremely small, and there exists a pronounced mixing between the Jeff = 1/2 and Jeff = 3/2 states. Moreover, our data reveal that the predicted Dirac degeneracy protected by the mirror-symmetry, which was theoretically suggested to be the key to realize the non-trivial topological properties, is actually lifted in perovskite SrIrO3 thin films. Our findings pose strong constraints on the current theoretical models for the 5d iridates.
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16
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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}. PHYSICAL REVIEW LETTERS 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] [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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17
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He J, Hogan T, Mion TR, Hafiz H, He Y, Denlinger JD, Mo SK, Dhital C, Chen X, Lin Q, Zhang Y, Hashimoto M, Pan H, Lu DH, Arita M, Shimada K, Markiewicz RS, Wang Z, Kempa K, Naughton MJ, Bansil A, Wilson SD, He RH. Spectroscopic evidence for negative electronic compressibility in a quasi-three-dimensional spin-orbit correlated metal. NATURE MATERIALS 2015; 14:577-582. [PMID: 25915033 DOI: 10.1038/nmat4273] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 03/19/2015] [Indexed: 06/04/2023]
Abstract
Negative compressibility is a sign of thermodynamic instability of open or non-equilibrium systems. In quantum materials consisting of multiple mutually coupled subsystems, the compressibility of one subsystem can be negative if it is countered by positive compressibility of the others. Manifestations of this effect have so far been limited to low-dimensional dilute electron systems. Here, we present evidence from angle-resolved photoemission spectroscopy (ARPES) for negative electronic compressibility (NEC) in the quasi-three-dimensional (3D) spin-orbit correlated metal (Sr1-xLax)3Ir2O7. Increased electron filling accompanies an anomalous decrease of the chemical potential, as indicated by the overall movement of the deep valence bands. Such anomaly, suggestive of NEC, is shown to be primarily driven by the lowering in energy of the conduction band as the correlated bandgap reduces. Our finding points to a distinct pathway towards an uncharted territory of NEC featuring bulk correlated metals with unique potential for applications in low-power nanoelectronics and novel metamaterials.
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Affiliation(s)
- Junfeng He
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - T Hogan
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Thomas R Mion
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - H Hafiz
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
| | - Y He
- Stanford Synchrotron Radiation Lightsource &Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J D Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - S-K Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C Dhital
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - X Chen
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Qisen Lin
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Y Zhang
- International Center for Quantum Materials, Peking University, Beijing 100871, China
| | - M Hashimoto
- Stanford Synchrotron Radiation Lightsource &Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - H Pan
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - D H Lu
- Stanford Synchrotron Radiation Lightsource &Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - M Arita
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Hiroshima 739-0046, Japan
| | - K Shimada
- Hiroshima Synchrotron Radiation Center, Hiroshima University, Hiroshima 739-0046, Japan
| | - R S Markiewicz
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
| | - Z Wang
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - K Kempa
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - M J Naughton
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - A Bansil
- Physics Department, Northeastern University, Boston, Massachusetts 02115, USA
| | - S D Wilson
- 1] Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA [2] Materials Department, University of California Santa Barbara, Santa Barbara, California 93106, USA
| | - Rui-Hua He
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
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18
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Fermi arcs vs. Fermi pockets in electron-doped perovskite iridates. Sci Rep 2015; 5:8533. [PMID: 25704850 PMCID: PMC4336940 DOI: 10.1038/srep08533] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 01/23/2015] [Indexed: 11/09/2022] Open
Abstract
We report on an angle resolved photoemission (ARPES) study of bulk electron-doped perovskite iridate, (Sr1−xLax)3Ir2O7. Fermi surface pockets are observed with a total electron count in keeping with that expected from La substitution. Depending on the energy and polarization of the incident photons, these pockets show up in the form of disconnected “Fermi arcs”, reminiscent of those reported recently in surface electron-doped Sr2IrO4. Our observed spectral variation is consistent with the coexistence of an electronic supermodulation with structural distortion in the system.
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19
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de la Torre A, Hunter EC, Subedi A, McKeown Walker S, Tamai A, Kim TK, Hoesch M, Perry RS, Georges A, Baumberger F. Coherent quasiparticles with a small fermi surface in lightly doped Sr(3)Ir(2)O(7). PHYSICAL REVIEW LETTERS 2014; 113:256402. [PMID: 25554897 DOI: 10.1103/physrevlett.113.256402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Indexed: 06/04/2023]
Abstract
We characterize the electron doping evolution of (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} by means of angle-resolved photoemission. Concomitant with the metal insulator transition around x≈0.05 we find the emergence of coherent quasiparticle states forming a closed small Fermi surface of volume 3x/2, where x is the independently measured La concentration. The quasiparticle weight Z remains large along the entire Fermi surface, consistent with the moderate renormalization of the low-energy dispersion, and no pseudogap is observed. This indicates a conventional, weakly correlated Fermi liquid state with a momentum independent residue Z≈0.5 in lightly doped Sr_{3}Ir_{2}O_{7}.
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Affiliation(s)
- A de la Torre
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - E C Hunter
- School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Mayfield Road, Edinburgh EH9 2TT, United Kingdom
| | - A Subedi
- Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau Cedex, France
| | - S McKeown Walker
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A Tamai
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - T K Kim
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - M Hoesch
- Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
| | - R S Perry
- London Centre for Nanotechnology and UCL Centre for Materials Discovery, University College London, London WC1E 6BT, United Kingdom
| | - A Georges
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland and Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau Cedex, France and Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
| | - F Baumberger
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland and Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, United Kingdom
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20
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Hitosugi T, Shimizu R, Ohsawa T, Iwaya K. Scanning Tunneling Microscopy/Spectroscopy on Perovskite Oxide Thin Films Deposited In Situ. CHEM REC 2014; 14:935-43. [DOI: 10.1002/tcr.201402041] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Indexed: 11/10/2022]
Affiliation(s)
- Taro Hitosugi
- Advanced Institute for Materials Research (AIMR); Tohoku University; Sendai 980-8577 Japan
- PRESTO; Japan Science and Technology Agency; Tokyo 102-0076 Japan
| | - Ryota Shimizu
- Advanced Institute for Materials Research (AIMR); Tohoku University; Sendai 980-8577 Japan
| | - Takeo Ohsawa
- Advanced Institute for Materials Research (AIMR); Tohoku University; Sendai 980-8577 Japan
| | - Katsuya Iwaya
- Advanced Institute for Materials Research (AIMR); Tohoku University; Sendai 980-8577 Japan
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21
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Stöger B, Hieckel M, Mittendorfer F, Wang Z, Fobes D, Peng J, Mao Z, Schmid M, Redinger J, Diebold U. High chemical activity of a perovskite surface: reaction of CO with Sr(3)Ru(2)O(7). PHYSICAL REVIEW LETTERS 2014; 113:116101. [PMID: 25259988 DOI: 10.1103/physrevlett.113.116101] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Indexed: 06/03/2023]
Abstract
Adsorption of CO at the Sr(3)Ru(2)O(7)(001) surface was studied with low-temperature scanning tunneling microscopy (STM) and density functional theory. In situ cleaved single crystals terminate in an almost perfect SrO surface. At 78 K, CO first populates impurities and then adsorbs above the apical surface O with a binding energy E(ads)=-0.7 eV. Above 100 K, this physisorbed CO replaces the surface O, forming a bent CO(2) with the C end bound to the Ru underneath. The resulting metal carboxylate (Ru-COO) can be desorbed by STM manipulation. A low activation (0.2 eV) and high binding (-2.2 eV) energy confirm a strong reaction between CO and regular surface sites of Sr(3)Ru(2)O(7); likely, this reaction causes the "UHV aging effect" reported for this and other perovskite oxides.
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Affiliation(s)
- Bernhard Stöger
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria
| | - Marcel Hieckel
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria and Center for Computational Materials Science, Vienna University of Technology, Gußhausstraße 25-25a, A-1040 Vienna, Austria
| | - Florian Mittendorfer
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria and Center for Computational Materials Science, Vienna University of Technology, Gußhausstraße 25-25a, A-1040 Vienna, Austria
| | - Zhiming Wang
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria
| | - David Fobes
- Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
| | - Jin Peng
- Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
| | - Zhiqiang Mao
- Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA
| | - Michael Schmid
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria
| | - Josef Redinger
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria and Center for Computational Materials Science, Vienna University of Technology, Gußhausstraße 25-25a, A-1040 Vienna, Austria
| | - Ulrike Diebold
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria
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22
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Zocco DA, Hamlin JJ, White BD, Kim BJ, Jeffries JR, Weir ST, Vohra YK, Allen JW, Maple MB. Persistent non-metallic behavior in Sr2IrO4 and Sr3Ir2O7 at high pressures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:255603. [PMID: 24888379 DOI: 10.1088/0953-8984/26/25/255603] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Iridium-based 5d transition-metal oxides are attractive candidates for the study of correlated electronic states due to the interplay of enhanced crystal-field, Coulomb and spin-orbit interaction energies. At ambient pressure, these conditions promote a novel Jeff = 1/2 Mott-insulating state, characterized by a gap of the order of ~0.1 eV. We present high-pressure electrical resistivity measurements of single crystals of Sr2IrO4 and Sr3Ir2O7. While no indications of a pressure-induced metallic state up to 55 GPa were found in Sr2IrO4, a strong decrease of the gap energy and of the resistance of Sr3Ir2O7 between ambient pressure and 104 GPa confirm that this compound is in the proximity of a metal-insulator transition.
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23
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Kim HJ, Lee JH, Cho JH. Antiferromagnetic Slater insulator phase of Na₂IrO₃. Sci Rep 2014; 4:5253. [PMID: 24918968 PMCID: PMC4052719 DOI: 10.1038/srep05253] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 05/20/2014] [Indexed: 11/20/2022] Open
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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24
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Kahk JM, Poll CG, Oropeza FE, Ablett JM, Céolin D, Rueff JP, Agrestini S, Utsumi Y, Tsuei KD, Liao YF, Borgatti F, Panaccione G, Regoutz A, Egdell RG, Morgan BJ, Scanlon DO, Payne DJ. Understanding the electronic structure of IrO2 using hard-X-ray photoelectron spectroscopy and density-functional theory. PHYSICAL REVIEW LETTERS 2014; 112:117601. [PMID: 24702416 DOI: 10.1103/physrevlett.112.117601] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Indexed: 05/27/2023]
Abstract
The electronic structure of IrO2 has been investigated using hard x-ray photoelectron spectroscopy and density-functional theory. Excellent agreement is observed between theory and experiment. We show that the electronic structure of IrO2 involves crystal field splitting of the iridium 5d orbitals in a distorted octahedral field. The behavior of IrO2 closely follows the theoretical predictions of Goodenough for conductive rutile-structured oxides [J. B. Goodenough, J. Solid State Chem. 3, 490 (1971).
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Affiliation(s)
- J M Kahk
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | - C G Poll
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | - F E Oropeza
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | - J M Ablett
- Synchrotron SOLEIL, L'Orme des Merisiers, BP 48 Saint-Aubin, 91192 Gif-sur-Yvette, France
| | - D Céolin
- Synchrotron SOLEIL, L'Orme des Merisiers, BP 48 Saint-Aubin, 91192 Gif-sur-Yvette, France
| | - J-P Rueff
- Synchrotron SOLEIL, L'Orme des Merisiers, BP 48 Saint-Aubin, 91192 Gif-sur-Yvette, France
| | - S Agrestini
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187 Dresden, Germany
| | - Y Utsumi
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzerstr. 40, 01187 Dresden, Germany
| | - K D Tsuei
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - Y F Liao
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - F Borgatti
- Consiglio Nazionale delle Ricerche, Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), via P. Gobetti n.101, I-40129 Bologna, Italy
| | - G Panaccione
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
| | - A Regoutz
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - R G Egdell
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - B J Morgan
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - D O Scanlon
- University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ, United Kingdom and Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - D J Payne
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
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25
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Dhital C, Hogan T, Zhou W, Chen X, Ren Z, Pokharel M, Okada Y, Heine M, Tian W, Yamani Z, Opeil C, Helton JS, Lynn JW, Wang Z, Madhavan V, Wilson SD. Carrier localization and electronic phase separation in a doped spin-orbit-driven Mott phase in Sr₃(Ir(1-x)Ru(x))₂O₇. Nat Commun 2014; 5:3377. [PMID: 24566714 DOI: 10.1038/ncomms4377] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Accepted: 02/04/2014] [Indexed: 11/09/2022] Open
Abstract
Interest in many strongly spin-orbit-coupled 5d-transition metal oxide insulators stems from mapping their electronic structures to a J(eff)=1/2 Mott phase. One of the hopes is to establish their Mott parent states and explore these systems' potential of realizing novel electronic states upon carrier doping. However, once doped, little is understood regarding the role of their reduced Coulomb interaction U relative to their strongly correlated 3d-electron cousins. Here we show that, upon hole-doping a candidate J(eff)=1/2 Mott insulator, carriers remain localized within a nanoscale phase-separated ground state. A percolative metal-insulator transition occurs with interplay between localized and itinerant regions, stabilizing an antiferromagnetic metallic phase beyond the critical region. Our results demonstrate a surprising parallel between doped 5d- and 3d-electron Mott systems and suggest either through the near-degeneracy of nearby electronic phases or direct carrier localization that U is essential to the carrier response of this doped spin-orbit Mott insulator.
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Affiliation(s)
- Chetan Dhital
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Tom Hogan
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Wenwen Zhou
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Xiang Chen
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Zhensong Ren
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Mani Pokharel
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Yoshinori Okada
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - M Heine
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Wei Tian
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA
| | - Z Yamani
- Chalk River Laboratories, Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, Canada K0J 1P0
| | - C Opeil
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - J S Helton
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - J W Lynn
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Vidya Madhavan
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Stephen D Wilson
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
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26
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Li G, Li Q, Pan M, Hu B, Chen C, Teng J, Diao Z, Zhang J, Jin R, Plummer EW. Atomic-scale fingerprint of Mn dopant at the surface of Sr₃(Ru₁-xMnx)₂O₇. Sci Rep 2013; 3:2882. [PMID: 24108411 PMCID: PMC3794371 DOI: 10.1038/srep02882] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 09/13/2013] [Indexed: 11/09/2022] Open
Abstract
Chemical doping in materials is known to give rise to emergent phenomena. These phenomena are extremely difficult to predict a priori, because electron-electron interactions are entangled with local environment of assembled atoms. Scanning tunneling microscopy and low energy electron diffraction are combined to investigate how the local electronic structure is correlated with lattice distortion on the surface of Sr3(Ru1-xMnx)2O7, which has double-layer building blocks formed by (Ru/Mn)O6 octahedra with rotational distortion. The presence of doping-dependent tilt distortion of (Ru/Mn)O6 octahedra at the surface results in a C2v broken symmetry in contrast with the bulk C4v counterpart. It also enables us to observe two Mn sites associated with the octahedral rotation in the bulk through the "chirality" of local electronic density of states surrounding Mn, which is randomly distributed. These results serve as fingerprint of chemical doping on the atomic scale.
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Affiliation(s)
- Guorong Li
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Qing Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China
| | - Minghu Pan
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Biao Hu
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Chen Chen
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Jing Teng
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Zhenyu Diao
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Jiandi Zhang
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Rongying Jin
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - E. W. Plummer
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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