1
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Gozlinski T, Henn M, Wolf T, Le Tacon M, Schmalian J, Wulfhekel W. Bosonic excitation spectra of superconductingBi2Sr2CaCu2O8+δandYBa2Cu3O6+xextracted from scanning tunneling spectra. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:175601. [PMID: 38194720 DOI: 10.1088/1361-648x/ad1ca8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/09/2024] [Indexed: 01/11/2024]
Abstract
A detailed interpretation of scanning tunneling spectra obtained on unconventional superconductors enables one to gain information on the pairing boson. Decisive for this approach are inelastic tunneling events. Due to the lack of momentum conservation in tunneling from or to the sharp tip, those are enhanced in the geometry of a scanning tunneling microscope compared to planar tunnel junctions. This work extends the method of obtaining the bosonic excitation spectrum by deconvolution from tunneling spectra to nodald-wave superconductors. In particular, scanning tunneling spectra of slightly underdopedBi2Sr2CaCu2O8+δwith aTcof 82 K and optimally dopedYBa2Cu3O6+xwith aTcof 92 K reveal a resonance mode in their bosonic excitation spectrum atΩres≈63 meVandΩres≈61 meVrespectively. In both cases, the overall shape of the bosonic excitation spectrum is indicative of predominant spin scattering with a resonant mode atΩres<2Δand overdamped spin fluctuations for energies larger than 2Δ. To perform the deconvolution of the experimental data, we implemented an efficient iterative algorithm that significantly enhances the reliability of our analysis.
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Affiliation(s)
- Thomas Gozlinski
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Mirjam Henn
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Thomas Wolf
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Matthieu Le Tacon
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Jörg Schmalian
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
- Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
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2
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Tang T, Moritz B, Peng C, Shen ZX, Devereaux TP. Traces of electron-phonon coupling in one-dimensional cuprates. Nat Commun 2023; 14:3129. [PMID: 37253739 DOI: 10.1038/s41467-023-38408-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 04/26/2023] [Indexed: 06/01/2023] Open
Abstract
The appearance of certain spectral features in one-dimensional (1D) cuprate materials has been attributed to a strong, extended attractive coupling between electrons. Here, using time-dependent density matrix renormalization group methods on a Hubbard-extended Holstein model, we show that extended electron-phonon (e-ph) coupling presents an obvious choice to produce such an attractive interaction that reproduces the observed spectral features and doping dependence seen in angle-resolved photoemission experiments: diminished 3kF spectral weight, prominent spectral intensity of a holon-folding branch, and the correct holon band width. While extended e-ph coupling does not qualitatively alter the ground state of the 1D system compared to the Hubbard model, it quantitatively enhances the long-range superconducting correlations and suppresses spin correlations. Such an extended e-ph interaction may be an important missing ingredient in describing the physics of the structurally similar two-dimensional high-temperature superconducting layered cuprates, which may tip the balance between intertwined orders in favor of uniform d-wave superconductivity.
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Affiliation(s)
- Ta Tang
- Department of Applied Physics, Stanford University, California, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA
| | - Brian Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA
| | - Cheng Peng
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA
| | - Zhi-Xun Shen
- Department of Applied Physics, Stanford University, California, 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA
- Department of Physics, Stanford University, Stanford, CA, 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA
| | - Thomas P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, 94025, USA.
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA.
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA.
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3
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Wu X, Néel N, Brandbyge M, Kröger J. Enhancement of Graphene Phonon Excitation by a Chemically Engineered Molecular Resonance. PHYSICAL REVIEW LETTERS 2023; 130:116201. [PMID: 37001107 DOI: 10.1103/physrevlett.130.116201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/21/2023] [Indexed: 06/19/2023]
Abstract
The abstraction of pyrrolic hydrogen from a single phthalocyanine on graphene turns the molecule into a sensitive probe for graphene phonons. The inelastic electron transport measured with a scanning tunneling microscope across the molecular adsorbate and graphene becomes strongly enhanced for a graphene out-of-plane acoustic phonon mode. Supporting density functional and transport calculations elucidate the underlying physical mechanism. A molecular orbital resonance close to the Fermi energy controls the inelastic current while specific phonon modes of graphene are magnified due to their coupling to symmetry-equivalent vibrational quanta of the molecule.
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Affiliation(s)
- Xiaocui Wu
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Nicolas Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Mads Brandbyge
- Center of Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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4
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Zhang J, Wu H, Zhao G, Han L, Zhang J. A Review on Strain Study of Cuprate Superconductors. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12193340. [PMID: 36234468 PMCID: PMC9565469 DOI: 10.3390/nano12193340] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 06/13/2023]
Abstract
Cuprate superconductors have attracted extensive attention due to their broad promising application prospects. Among the factors affecting superconductivity, the effect of strain cannot be ignored, which can significantly enhance or degrade superconductivity. In this review, we discuss and summarize the methods of applying strain to cuprate superconductors, strain measurement techniques, and the influence of strain on superconductivity. Among them, we pay special attention to the study of strain in high-temperature superconducting (HTS) films and coating. We expect this review can guide further research in the field of cuprate superconductors.
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Affiliation(s)
- Jian Zhang
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
- Key Laboratory of Spin Electron and Nanomaterials of Anhui Higher Education Institutes, Suzhou University, Suzhou 234000, China
| | - Haiyan Wu
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
- Key Laboratory of Spin Electron and Nanomaterials of Anhui Higher Education Institutes, Suzhou University, Suzhou 234000, China
| | - Guangzhen Zhao
- Key Laboratory of Spin Electron and Nanomaterials of Anhui Higher Education Institutes, Suzhou University, Suzhou 234000, China
| | - Lu Han
- Key Laboratory of Spin Electron and Nanomaterials of Anhui Higher Education Institutes, Suzhou University, Suzhou 234000, China
| | - Jun Zhang
- School of Pharmacy, Dali University, Dali 671000, China
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5
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Fledgling Quantum Spin Hall Effect in Pseudo Gap Phase of Bi2212. Symmetry (Basel) 2022. [DOI: 10.3390/sym14081746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We studied the emergence of the quantum spin Hall (QSH) states for the pseudo-gap (PG) phase of Bi2212 bilayer system, assumed to be D-density wave (DDW) ordered, starting with a strong Rashba spin-orbit coupling (SOC) armed, and the time reversal symmetry (TRS) complaint Bloch Hamiltonian. The presence of strong SOC gives rise to non-trivial, spin-momentum locked spin texture tunable by electric field. The emergence of quantum anomalous Hall effect with TRS broken Chiral DDW Hamiltonian of Das Sarma et al. is found to be possible.
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6
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Sheng S, Oeter AC, Abdo M, Lichtenberg K, Hentschel M, Loth S. Launching Coherent Acoustic Phonon Wave Packets with Local Femtosecond Coulomb Forces. PHYSICAL REVIEW LETTERS 2022; 129:043001. [PMID: 35939022 DOI: 10.1103/physrevlett.129.043001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Generation and manipulation of coherent acoustic phonons enables ultrafast control of solids and has been exploited for applications in various acoustic devices. We show that localized coherent acoustic phonon wave packets can be launched by ultrafast Coulomb forces in a scanning tunneling microscope (STM) using tip-enhanced terahertz electric fields. The wave packets propagate at the speed of the longitudinal acoustic phonon, creating standing waves up to 0.26 THz for a 6.4 nm thin Au film on mica. The ultrafast lattice displacement can be as large as 5 pm and is precisely controlled by varying the tip-sample distance. This nonthermal femtosecond Coulomb-force-based excitation mechanism is applicable in nano-optomechanics for advanced terahertz engineering and opens new perspectives in exploiting coherent phonons at the atomic scale.
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Affiliation(s)
- Shaoxiang Sheng
- University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
| | - Anne-Catherine Oeter
- University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
| | - Mohamad Abdo
- University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Kurt Lichtenberg
- University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
| | - Mario Hentschel
- University of Stuttgart, 4th Physics Institute and Research Center SCoPE, 70569 Stuttgart, Germany
| | - Sebastian Loth
- University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
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7
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Pesquera D, Fernández A, Khestanova E, Martin LW. Freestanding complex-oxide membranes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:383001. [PMID: 35779514 DOI: 10.1088/1361-648x/ac7dd5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/01/2022] [Indexed: 06/15/2023]
Abstract
Complex oxides show a vast range of functional responses, unparalleled within the inorganic solids realm, making them promising materials for applications as varied as next-generation field-effect transistors, spintronic devices, electro-optic modulators, pyroelectric detectors, or oxygen reduction catalysts. Their stability in ambient conditions, chemical versatility, and large susceptibility to minute structural and electronic modifications make them ideal subjects of study to discover emergent phenomena and to generate novel functionalities for next-generation devices. Recent advances in the synthesis of single-crystal, freestanding complex oxide membranes provide an unprecedented opportunity to study these materials in a nearly-ideal system (e.g. free of mechanical/thermal interaction with substrates) as well as expanding the range of tools for tweaking their order parameters (i.e. (anti-)ferromagnetic, (anti-)ferroelectric, ferroelastic), and increasing the possibility of achieving novel heterointegration approaches (including interfacing dissimilar materials) by avoiding the chemical, structural, or thermal constraints in synthesis processes. Here, we review the recent developments in the fabrication and characterization of complex-oxide membranes and discuss their potential for unraveling novel physicochemical phenomena at the nanoscale and for further exploiting their functionalities in technologically relevant devices.
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Affiliation(s)
- David Pesquera
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST Campus UAB, Bellaterra, Barcelona 08193, Spain
| | - Abel Fernández
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, United States of America
| | | | - Lane W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, United States of America
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
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8
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Evidence for unconventional superconductivity in twisted trilayer graphene. Nature 2022; 606:494-500. [PMID: 35705819 DOI: 10.1038/s41586-022-04715-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 04/01/2022] [Indexed: 11/08/2022]
Abstract
Magic-angle twisted trilayer graphene (MATTG) has emerged as a moiré material that exhibits strong electronic correlations and unconventional superconductivity1,2. However, local spectroscopic studies of this system are still lacking. Here we perform high-resolution scanning tunnelling microscopy and spectroscopy of MATTG that reveal extensive regions of atomic reconstruction favouring mirror-symmetric stacking. In these regions, we observe symmetry-breaking electronic transitions and doping-dependent band-structure deformations similar to those in magic-angle bilayers, as expected theoretically given the commonality of flat bands3,4. Most notably in a density window spanning two to three holes per moiré unit cell, the spectroscopic signatures of superconductivity are manifest as pronounced dips in the tunnelling conductance at the Fermi level accompanied by coherence peaks that become gradually suppressed at elevated temperatures and magnetic fields. The observed evolution of the conductance with doping is consistent with a gate-tunable transition from a gapped superconductor to a nodal superconductor, which is theoretically compatible with a sharp transition from a Bardeen-Cooper-Schrieffer superconductor to a Bose-Einstein-condensation superconductor with a nodal order parameter. Within this doping window, we also detect peak-dip-hump structures that suggest that superconductivity is driven by strong coupling to bosonic modes of MATTG. Our results will enable further understanding of superconductivity and correlated states in graphene-based moiré structures beyond twisted bilayers5.
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9
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Fan JQ, Yu XQ, Cheng FJ, Wang H, Wang R, Ma X, Hu XP, Zhang D, Ma XC, Xue QK, Song CL. Direct observation of nodeless superconductivity and phonon modes in electron-doped copper oxide Sr1-xNdxCuO2. Natl Sci Rev 2021; 9:nwab225. [PMID: 35530436 PMCID: PMC9070465 DOI: 10.1093/nsr/nwab225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 12/10/2021] [Accepted: 12/12/2021] [Indexed: 11/14/2022] Open
Abstract
The microscopic understanding of high-temperature superconductivity in cuprates has been hindered by the apparent complexity of crystal structures in these materials. We used scanning tunneling microscopy and spectroscopy to study the electron-doped copper oxide compound Sr1−xNdxCuO2, which has only bare cations separating the CuO2 planes and thus the simplest infinite-layer structure of all cuprate superconductors. Tunneling conductance spectra of the major CuO2 planes in the superconducting state revealed direct evidence for a nodeless pairing gap, regardless of variation of its magnitude with the local doping of trivalent neodymium. Furthermore, three distinct bosonic modes are observed as multiple peak-dip-hump features outside the superconducting gaps and their respective energies depend little on the spatially varying gaps. As well as the bosonic modes, with energies identical to those of the external, bending and stretching phonons of copper oxides, our findings reveal the origin of the bosonic modes in lattice vibrations rather than spin excitations.
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Affiliation(s)
- Jia-Qi Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Xue-Qing Yu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Fang-Jun Cheng
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Heng Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Ruifeng Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Xiaobing Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Xiao-Peng Hu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
| | - Ding Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
- Frontier Science Center for Quantum Information, Beijing100084, China
- Beijing Academy of Quantum Information Sciences, Beijing100193, China
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama351-0198, Japan
| | - Xu-Cun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
- Frontier Science Center for Quantum Information, Beijing100084, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
- Frontier Science Center for Quantum Information, Beijing100084, China
- Beijing Academy of Quantum Information Sciences, Beijing100193, China
- Southern University of Science and Technology, Shenzhen518055, China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing100084, China
- Frontier Science Center for Quantum Information, Beijing100084, China
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10
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Cai X, Li ZX, Yao H. Antiferromagnetism Induced by Bond Su-Schrieffer-Heeger Electron-Phonon Coupling: A Quantum Monte Carlo Study. PHYSICAL REVIEW LETTERS 2021; 127:247203. [PMID: 34951814 DOI: 10.1103/physrevlett.127.247203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/22/2021] [Accepted: 10/28/2021] [Indexed: 06/14/2023]
Abstract
Antiferromagnetism (AFM) such as Néel ordering is often closely related to Coulomb interactions such as Hubbard repulsion in two-dimensional (2D) systems. Whether Néel AFM ordering in two dimensions can be dominantly induced by electron-phonon couplings (EPC) has not been completely understood. Here, by employing numerically exact sign-problem-free quantum Monte Carlo (QMC) simulations, we show that bond Su-Schrieffer-Heeger (SSH) phonons with frequency ω and EPC constant λ can induce AFM ordering for a wide range of phonon frequency ω>ω_{c}. For ω<ω_{c}, a valence-bond-solid (VBS) order appears and there is a direct quantum phase transition between VBS and AFM phases at ω_{c}. The phonon mechanism of the AFM ordering is related to the fact that SSH phonons directly couple to electron hopping whose second-order process can induce an effective AFM spin exchange. Our results shall shed new light on understanding AFM ordering in correlated quantum materials.
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Affiliation(s)
- Xun Cai
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Zi-Xiang Li
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Hong Yao
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
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11
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Wang Y, Chen Z, Shi T, Moritz B, Shen ZX, Devereaux TP. Phonon-Mediated Long-Range Attractive Interaction in One-Dimensional Cuprates. PHYSICAL REVIEW LETTERS 2021; 127:197003. [PMID: 34797146 DOI: 10.1103/physrevlett.127.197003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/22/2021] [Indexed: 06/13/2023]
Abstract
Establishing a minimal microscopic model for cuprates is a key step towards the elucidation of a high-T_{c} mechanism. By a quantitative comparison with a recent in situ angle-resolved photoemission spectroscopy measurement in doped 1D cuprate chains, our simulation identifies a crucial contribution from long-range electron-phonon coupling beyond standard Hubbard models. Using reasonable ranges of coupling strengths and phonon energies, we obtain a strong attractive interaction between neighboring electrons, whose strength is comparable to experimental observations. Nonlocal couplings play a significant role in the mediation of neighboring interactions. Considering the structural and chemical similarity between 1D and 2D cuprate materials, this minimal model with long-range electron-phonon coupling will provide important new insights on cuprate high-T_{c} superconductivity and related quantum phases.
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Affiliation(s)
- Yao Wang
- Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29631, USA
| | - Zhuoyu Chen
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Tao Shi
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Brian Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Zhi-Xun Shen
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Departments of Physics and Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Thomas P Devereaux
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
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12
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Direct probing of phonon mode specific electron-phonon scatterings in two-dimensional semiconductor transition metal dichalcogenides. Nat Commun 2021; 12:4520. [PMID: 34312387 PMCID: PMC8313722 DOI: 10.1038/s41467-021-24875-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/13/2021] [Indexed: 11/18/2022] Open
Abstract
Electron–phonon scatterings in solid-state systems are pivotal processes in determining many key physical quantities such as charge carrier mobilities and thermal conductivities. Here, we report direct probing of phonon mode specific electron–phonon scatterings in layered semiconducting transition metal dichalcogenides WSe2, MoSe2, WS2, and MoS2 through inelastic electron tunneling spectroscopy measurements, quantum transport simulations, and density functional calculation. We experimentally and theoretically characterize momentum-conserving single- and two-phonon electron–phonon scatterings involving up to as many as eight individual phonon modes in mono- and bilayer films, among which transverse, longitudinal acoustic and optical, and flexural optical phonons play significant roles in quantum charge flows. Moreover, the layer-number sensitive higher-order inelastic electron–phonon scatterings, which are confirmed to be generic in all four semiconducting layers, can be attributed to differing electronic structures, symmetry, and quantum interference effects during the scattering processes in the ultrathin semiconducting films. Electron–phonon scattering events in solid-state systems determine key physical quantities. Here, the authors probe momentum-conserving single- and two-phonon electron–phonon scattering events involving up to as many as eight individual phonon modes in 2D semiconductors.
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13
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Superconducting coherence length of hole-doped cuprates obtained from electron-boson spectral density function. Sci Rep 2021; 11:11668. [PMID: 34083645 PMCID: PMC8175355 DOI: 10.1038/s41598-021-91163-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 05/24/2021] [Indexed: 11/08/2022] Open
Abstract
Electron–boson spectral density functions (EBSDFs) can be obtained from measured spectra using various spectroscopic techniques, including optical spectroscopy. EBSDFs, known as glue functions, are suggested to have a magnetic origin. Here, we investigated EBSDFs obtained from the measured optical spectra of hole-doped cuprates with wide doping levels, from underdoped to overdoped cuprates. The average frequency of an EBSDF provides the timescale for the spin fluctuations to form Cooper pairs. This timescale is directly associated with retarded interactions between electrons. Using this timescale and Fermi velocity, a reasonable superconducting coherence length, which reflects the size of the Cooper pair, can be extracted. The obtained coherence lengths were consistent with those measured via other experimental techniques. Therefore, the formation of Cooper pairs in cuprates can be explained by spin fluctuations, the timescales of which appear in EBSDFs. Consequently, EBSDFs provide crucial information on the timescale of the microscopic mechanism of Cooper pair formation.
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14
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Bian K, Gerber C, Heinrich AJ, Müller DJ, Scheuring S, Jiang Y. Scanning probe microscopy. ACTA ACUST UNITED AC 2021. [DOI: 10.1038/s43586-021-00033-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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15
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Role of molecule-electrode coupling strength in inducing inelastic transmission spectra of Hf@C28. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Yin JX, Shumiya N, Mardanya S, Wang Q, Zhang SS, Tien HJ, Multer D, Jiang Y, Cheng G, Yao N, Wu S, Wu D, Deng L, Ye Z, He R, Chang G, Liu Z, Jiang K, Wang Z, Neupert T, Agarwal A, Chang TR, Chu CW, Lei H, Hasan MZ. Fermion-boson many-body interplay in a frustrated kagome paramagnet. Nat Commun 2020; 11:4003. [PMID: 32778651 PMCID: PMC7417595 DOI: 10.1038/s41467-020-17464-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 07/01/2020] [Indexed: 11/09/2022] Open
Abstract
Kagome-nets, appearing in electronic, photonic and cold-atom systems, host frustrated fermionic and bosonic excitations. However, it is rare to find a system to study their fermion-boson many-body interplay. Here we use state-of-the-art scanning tunneling microscopy/spectroscopy to discover unusual electronic coupling to flat-band phonons in a layered kagome paramagnet, CoSn. We image the kagome structure with unprecedented atomic resolution and observe the striking bosonic mode interacting with dispersive kagome electrons near the Fermi surface. At this mode energy, the fermionic quasi-particle dispersion exhibits a pronounced renormalization, signaling a giant coupling to bosons. Through the self-energy analysis, first-principles calculation, and a lattice vibration model, we present evidence that this mode arises from the geometrically frustrated phonon flat-band, which is the lattice bosonic analog of the kagome electron flat-band. Our findings provide the first example of kagome bosonic mode (flat-band phonon) in electronic excitations and its strong interaction with fermionic degrees of freedom in kagome-net materials.
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Affiliation(s)
- J-X Yin
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
| | - Nana Shumiya
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Sougata Mardanya
- Department of Physics, National Cheng Kung University, 701, Tainan, Taiwan
| | - Qi Wang
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices, Renmin University of China, 100872, Beijing, China
| | - Songtian S Zhang
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Hung-Ju Tien
- Department of Physics, National Cheng Kung University, 701, Tainan, Taiwan
| | - Daniel Multer
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Yuxiao Jiang
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Guangming Cheng
- Princeton Institute for Science and Technology of Materials (PRISM), Princeton University, Princeton, NJ, 08544, USA
| | - Nan Yao
- Princeton Institute for Science and Technology of Materials (PRISM), Princeton University, Princeton, NJ, 08544, USA
| | - Shangfei Wu
- Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Desheng Wu
- Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Liangzi Deng
- Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX, 77204-5002, USA
| | - Zhipeng Ye
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX, 79409, USA
| | - Rui He
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX, 79409, USA
| | - Guoqing Chang
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Zhonghao Liu
- State Key Laboratory of Functional Materials for Informatics and Center for Excellence in Superconducting Electronics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 200050, Shanghai, China
| | - Kun Jiang
- Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA
| | - Ziqiang Wang
- Department of Physics, Boston College, Chestnut Hill, MA, 02467, USA
| | - Titus Neupert
- Department of Physics, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
| | - Amit Agarwal
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Tay-Rong Chang
- Department of Physics, National Cheng Kung University, 701, Tainan, Taiwan
- Center for Quantum Frontiers of Research and Technology (QFort), 701, Tainan, Taiwan
- Physics Division, National Center for Theoretical Sciences, 30013, Hsinchu, Taiwan
| | - Ching-Wu Chu
- Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX, 77204-5002, USA
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Hechang Lei
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices, Renmin University of China, 100872, Beijing, China
| | - M Zahid Hasan
- Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
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Xu X, Zhang S, Zhu X, Guo J. Superconductivity enhancement in FeSe/SrTiO 3: a review from the perspective of electron-phonon coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:343003. [PMID: 32241002 DOI: 10.1088/1361-648x/ab85f0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
Single-layer FeSe films grown on SrTiO3, with the highest superconducting transition temperature (TC) among all the iron-based superconductors, serves as an ideal platform for studying the microscopic mechanisms of high-TCsuperconductivity. The significant role of interfacial coupling has been widely recognized, while the precise nature of theTCenhancement remains open. In this review, we focus on the investigations of the interfacial coupling in FeSe/SrTiO3from the perspective of electron-phonon coupling (EPC). The main content will include an overview of the experimental measurements associated with different theoretical models and arguments about the EPC. Especially, besides the discussions of EPC based on the measurements of electronic states, we will emphasize the analyses based on phonon measurements. A uniform picture about the nature of the EPC and its relation to theTCenhancement in FeSe/SrTiO3has still not achieved, which should be the key for further studies aiming to the in-depth understanding of high-TCsuperconductivity and the discovery of new superconductors with even enhancedTC.
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Affiliation(s)
- Xiaofeng Xu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Shuyuan Zhang
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, United States of America
| | - Xuetao Zhu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Jiandong Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
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18
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Nakajima R, Midorikawa N. Topic extraction to provide an overview of research activities: The case of the high-temperature superconductor and simulation and modelling. J Inf Sci 2020. [DOI: 10.1177/0165551520920794] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
For those who are not experts in a particular scientific field, it is difficult to understand scientific research trends. Although studies on the extraction of research trends have been conducted, most focus on extracting global trends from large-scale data, and the methods are often complicated. The purpose of this study is to develop a method of obtaining overviews of a scientific field for non-experts by capturing research trends simply and then to verify the method. To extract research topics which should express research trends, text analysis was performed using abstracts over 12 years of articles on high-temperature superconductors. We characterised three topics for the extracted word groups that frequently occurred. For these topics, we studied their appropriateness using a method that has been little used: examining research articles, review literature and co-citations among research articles used to extract the words, comparisons with controlled index terms assigned to the articles and confirming that there were no contradictions. Based on the established method, we have also applied this method to another research field: ‘simulation and modelling’. Although the method used in this article is simple, important topics were extracted, and the relations with the original articles are clear, which can lead to further investigation of the extracted topics.
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Affiliation(s)
- Ritsuko Nakajima
- Graduate School of Library, Information and Media Studies, University of Tsukuba, Japan
| | - Nobuyuki Midorikawa
- Faculty of Library, Information and Media Science, University of Tsukuba, Japan
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19
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Chen C, Liu C, Liu Y, Wang J. Bosonic Mode and Impurity-Scattering in Monolayer Fe(Te,Se) High-Temperature Superconductors. NANO LETTERS 2020; 20:2056-2061. [PMID: 32045257 DOI: 10.1021/acs.nanolett.0c00028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electron pairing mechanism has always been one of the most challenging problems in high-temperature superconductors. Fe(Te,Se), as the superconductor with intrinsic topological property, may host Majorana bound states and has attracted tremendous interest. While in bulk Fe(Te,Se) the pairing mechanism has been experimentally investigated, it remains little understood in its two-dimensional limit counterpart. Here, by in situ scanning tunneling spectroscopy, we show clear evidence of the bosonic mode Ω beyond the superconducting gap Δ in monolayer FeTe0.5Se0.5/SrTiO3(001) high-temperature superconductor. Statistically, Ω shows an obvious anticorrelation with Δ and appears below 2Δ, consistent with the spin-excitation nature. Furthermore, the in-gap bound states induced by two types of magnetically different impurities support the sign-reversing pairing scenario. Our results not only suggest that the spin-excitation-like bosonic mode within a sign-reversing pairing plays an essential role in monolayer FeTe0.5Se0.5/SrTiO3(001) but also offer the crucial information for investigating the high-temperature superconductivity in interfacial iron selenides.
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Affiliation(s)
- Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P.R. China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, P.R. China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, P.R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P.R. China
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20
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Li T, Yao DW. Why the anti-nodal quasiparticle dispersion is so flat in the superconducting cuprates? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:095601. [PMID: 33242846 DOI: 10.1088/1361-648x/abce42] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The emergence of the coherent quasiparticle peak and the development of the peak-dip-hump structure in the anti-nodal region below T c is the most prominent non-BCS signature of the under-doped high-T c cuprates, in which no coherent quasiparticle can be defined in the anti-nodal region above T c. The peak-dip-hump structure has been commonly interpreted as the result of the coupling of the electron to some Bosonic mode. However, such an electron-Boson coupling picture does not answer the question of why the quasiparticle dispersion is so flat in the anti-nodal region, a behavior totally unexpected for Bogoliubov quasiparticle in a d-wave BCS superconductor. Here we show that the sharp quasiparticle peak in the anti-nodal region should be understood as a new pole in the electron Green's function generated by the strong coupling of the electron to diffusive spin fluctuation around the antiferromagnetic wave vector Q = (π, π), rather than a nearly free Bogoliubov quasiparticle in a d-wave BCS superconductor. More specifically, we find that the normal self-energy of the electron from the scattering with the diffusive spin fluctuation manifests itself mainly as a level repulsion effect and is responsible for the reduction of both the quasiparticle dispersion and the quasiparticle dissipation rate in the anti-nodal region. We argue that the peak-dip separation in the anti-nodal spectrum should not be interpreted as the energy of the pairing glue.
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Affiliation(s)
- Tao Li
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
| | - Da-Wei Yao
- Department of Physics, Renmin University of China, Beijing 100872, People's Republic of China
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21
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De B, Muralidharan B. Manipulation of non-linear heat currents in the dissipative Anderson-Holstein model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:035305. [PMID: 31469086 DOI: 10.1088/1361-648x/ab3f82] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The precise control of phonon heat currents will be of primary importance in emerging phononic devices. In this paper, a detailed analysis of electronically controled phonon transport is carried out using an Anderson-Holstein based dissipative quantum dot setup. We consider two relevant electronic bias situations: (a) a voltage bias in the absence of an electronic temperature gradient and (b) an electronic temperature gradient at zero voltage. It is shown that the direction of phonon transport in the non-linear regime is different in the two cases since the first case facilitates the accumulation of phonons in the dot and the second case leads to the absorption of phonons in the dot. In the linear regime, both the phonon and electronic transport get decoupled and Onsager's symmetry is verified. We explain the observed cumulative effects of voltage and electronic temperature gradients on the non-linear phonon currents by introducing a new transport coefficient that we term as the electron induced phonon thermal conductivity. It is demonstrated that under suitable operating conditions in Case (a) the dot can pump in phonons into the hotter phonon reservoirs and in Case (b) the dot can extract phonons out of the colder phonon reservoirs. Finally, as a corollary, we elaborate on how the non-linear electronic heat current can be stimulated and controlled by manipulating the temperature of the phonon reservoirs even under vanishing effective electronic charge flow.
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Affiliation(s)
- Bitan De
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India
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22
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Rossi M, Arpaia R, Fumagalli R, Moretti Sala M, Betto D, Kummer K, De Luca GM, van den Brink J, Salluzzo M, Brookes NB, Braicovich L, Ghiringhelli G. Experimental Determination of Momentum-Resolved Electron-Phonon Coupling. PHYSICAL REVIEW LETTERS 2019; 123:027001. [PMID: 31386544 DOI: 10.1103/physrevlett.123.027001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Indexed: 06/10/2023]
Abstract
We provide a novel experimental method to quantitatively estimate the electron-phonon coupling and its momentum dependence from resonant inelastic x-ray scattering (RIXS) spectra based on the detuning of the incident photon energy away from an absorption resonance. We apply it to the cuprate parent compound NdBa_{2}Cu_{3}O_{6} and find that the electronic coupling to the oxygen half-breathing phonon branch is strongest at the Brillouin zone boundary, where it amounts to ∼0.17 eV, in agreement with previous studies. In principle, this method is applicable to any absorption resonance suitable for RIXS measurements and will help to define the contribution of lattice vibrations to the peculiar properties of quantum materials.
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Affiliation(s)
- Matteo Rossi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Riccardo Arpaia
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden
| | - Roberto Fumagalli
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Marco Moretti Sala
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
| | - Davide Betto
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Kurt Kummer
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Gabriella M De Luca
- Dipartimento di Fisica "E. Pancini," Università degli Studi di Napoli "Federico II," Complesso Monte Sant'Angelo-Via Cinthia, I-80126 Napoli, Italy
- CNR-SPIN, Complesso Monte Sant'Angelo-Via Cinthia, I-80126 Napoli, Italy
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden, Germany
- Department of Physics, Technical University Dresden, D-01062 Dresden, Germany
| | - Marco Salluzzo
- CNR-SPIN, Complesso Monte Sant'Angelo-Via Cinthia, I-80126 Napoli, Italy
| | - Nicholas B Brookes
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Lucio Braicovich
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- ESRF-The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Giacomo Ghiringhelli
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
- CNR-SPIN, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
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23
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Patera LL, Queck F, Scheuerer P, Moll N, Repp J. Accessing a Charged Intermediate State Involved in the Excitation of Single Molecules. PHYSICAL REVIEW LETTERS 2019; 123:016001. [PMID: 31386418 DOI: 10.1103/physrevlett.123.016001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 05/02/2019] [Indexed: 06/10/2023]
Abstract
Intermediate states are elusive to many experimental techniques due to their short lifetimes. Here, by performing single-electron alternate charging scanning tunneling microscopy of molecules on insulators, we accessed a charged intermediate state involved in the rapid toggling of individual metal phthalocyanines deposited on NaCl films. By stabilizing the transient species, we reveal how electron injection into the lowest unoccupied molecular orbital leads to a pronounced change in the adsorption geometry, characterized by a different azimuthal orientation. This observation allows clarifying the nature of the toggling process, unveiling the role of transient ionic states involved into fundamental processes occurring at interfaces.
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Affiliation(s)
- Laerte L Patera
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Fabian Queck
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Philipp Scheuerer
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Nikolaj Moll
- IBM Research-Zurich, 8803 Rüschlikon, Switzerland
| | - Jascha Repp
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
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24
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Liu C, Wang Z, Ye S, Chen C, Liu Y, Wang Q, Wang QH, Wang J. Detection of Bosonic Mode as a Signature of Magnetic Excitation in One-Unit-Cell FeSe on SrTiO 3. NANO LETTERS 2019; 19:3464-3472. [PMID: 31117746 DOI: 10.1021/acs.nanolett.9b00144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A "fingerprint" of Cooper pairing mediated by collective bosonic excitation mode is the reconstruction of the quasiparticle-density-of-states (DOS) spectrum with an additional "dip-hump" structure located outside the superconducting coherence peak. Here, we report an in situ scanning tunneling spectroscopy study of one-unit-cell (1-UC) FeSe film on a SrTiO3(001) substrate. In the quasiparticle-DOS spectrum, the bosonic excitation mode characterized by the dip-hump structure is detected outside the larger superconducting gap. Statistically, the excitation mode shows an anticorrelation with pairing strength in magnitude and yields an energy scale upper-bounded by twice the superconducting gap. The observation coincides with the characteristics of magnetic resonance in cuprates and iron-based superconductors. Furthermore, the local response of superconducting spectra to magnetically distinct Se defects all exhibits the induced in-gap quasiparticle bound states, indicating an unconventional sign-reversing pairing over the Fermi surface in 1-UC FeSe. These results clarify the magnetic nature of the bosonic excitation mode and reveal a signature of electron-magnetic-excitation coupling in 1-UC FeSe/SrTiO3(001) besides the previously established pairing channel of electron-phonon interaction.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Ziqiao Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Shusen Ye
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Cheng Chen
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | - Qingyan Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
| | | | - Jian Wang
- International Center for Quantum Materials, School of Physics , Peking University , Beijing 100871 , China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871 , China
- CAS Center for Excellence in Topological Quantum Computation , University of Chinese Academy of Sciences , Beijing 100190 , China
- Beijing Academy of Quantum Information Sciences , Beijing 100193 , China
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25
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Abstract
The role of electron-phonon interactions in iron-based superconductor is currently under debate with conflicting experimental reports on the isotope effect. To address this important issue, we employ the renormalization-group method to investigate the competition between electron-electron and electron-phonon interactions in these materials. The renormalization-group analysis shows that the ground state is a phonon-dressed unconventional superconductor: the dominant electronic interactions account for pairing mechanism while electron-phonon interactions are subdominant. Because of the phonon dressing, the isotope effect of the critical temperature can be normal or reversed, depending on whether the retarded intra- or inter-band interactions are altered upon isotope substitutions. The connection between the anomalous isotope effect and the unconventional pairing symmetry is discussed at the end.
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26
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He Y, Hashimoto M, Song D, Chen SD, He J, Vishik IM, Moritz B, Lee DH, Nagaosa N, Zaanen J, Devereaux TP, Yoshida Y, Eisaki H, Lu DH, Shen ZX. Rapid change of superconductivity and electron-phonon coupling through critical doping in Bi-2212. Science 2018; 362:62-65. [DOI: 10.1126/science.aar3394] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 07/30/2018] [Indexed: 11/02/2022]
Affiliation(s)
- Y. He
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - M. Hashimoto
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - D. Song
- National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
| | - S.-D. Chen
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - J. He
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - I. M. Vishik
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - B. Moritz
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - D.-H. Lee
- Department of Physics, University of California, Berkeley, CA 94720, USA
| | - N. Nagaosa
- Quantum-Phase Electronics Center, Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - J. Zaanen
- Instituut-Lorentz for Theoretical Physics, Leiden University, Leiden, Netherlands
| | - T. P. Devereaux
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Y. Yoshida
- National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
| | - H. Eisaki
- National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
| | - D. H. Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Z.-X. Shen
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA
- SIMES, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
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27
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Abstract
A central mystery in high-temperature superconductivity is the origin of the so-called strange metal (i.e., the anomalous conductor from which superconductivity emerges at low temperature). Measuring the dynamic charge response of the copper oxides, [Formula: see text], would directly reveal the collective properties of the strange metal, but it has never been possible to measure this quantity with millielectronvolt resolution. Here, we present a measurement of [Formula: see text] for a cuprate, optimally doped Bi2.1Sr1.9CaCu2O8+x (Tc = 91 K), using momentum-resolved inelastic electron scattering. In the medium energy range 0.1-2 eV relevant to the strange metal, the spectra are dominated by a featureless, temperature- and momentum-independent continuum persisting to the electronvolt energy scale. This continuum displays a simple power-law form, exhibiting q2 behavior at low energy and q2/ω2 behavior at high energy. Measurements of an overdoped crystal (Tc = 50 K) showed the emergence of a gap-like feature at low temperature, indicating deviation from power law form outside the strange-metal regime. Our study suggests the strange metal exhibits a new type of charge dynamics in which excitations are local to such a degree that space and time axes are decoupled.
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28
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Choi S, Johnston S, Jang WJ, Koepernik K, Nakatsukasa K, Ok JM, Lee HJ, Choi HW, Lee AT, Akbari A, Semertzidis YK, Bang Y, Kim JS, Lee J. Correlation of Fe-Based Superconductivity and Electron-Phonon Coupling in an FeAs/Oxide Heterostructure. PHYSICAL REVIEW LETTERS 2017; 119:107003. [PMID: 28949163 DOI: 10.1103/physrevlett.119.107003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Indexed: 06/07/2023]
Abstract
Interfacial phonons between iron-based superconductors (FeSCs) and perovskite substrates have received considerable attention due to the possibility of enhancing preexisting superconductivity. Using scanning tunneling spectroscopy, we studied the correlation between superconductivity and e-ph interaction with interfacial phonons in an iron-based superconductor Sr_{2}VO_{3}FeAs (T_{c}≈33 K) made of alternating FeSC and oxide layers. The quasiparticle interference measurement over regions with systematically different average superconducting gaps due to the e-ph coupling locally modulated by O vacancies in the VO_{2} layer, and supporting self-consistent momentum-dependent Eliashberg calculations provide a unique real-space evidence of the forward-scattering interfacial phonon contribution to the total superconducting pairing.
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Affiliation(s)
- Seokhwan Choi
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Steven Johnston
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Won-Jun Jang
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34051, Korea
| | | | - Ken Nakatsukasa
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Jong Mok Ok
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Hyun-Jung Lee
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Hyun Woo Choi
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Alex Taekyung Lee
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Alireza Akbari
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
- Asia Pacific Center for Theoretical Physics, Pohang 37673, Korea
| | - Yannis K Semertzidis
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Center for Axion and Precision Physics Research, Institute for Basic Science (IBS), Daejeon 34051, Korea
| | - Yunkyu Bang
- Department of Physics, Chonnam National University, Gwangju 61186, Korea
| | - Jun Sung Kim
- Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Jhinhwan Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
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29
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A New Landscape of Multiple Dispersion Kinks in a High-T c Cuprate Superconductor. Sci Rep 2017; 7:4830. [PMID: 28684868 PMCID: PMC5500550 DOI: 10.1038/s41598-017-04983-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 05/23/2017] [Indexed: 11/08/2022] Open
Abstract
Conventional superconductivity is caused by electron-phonon coupling. The discovery of high-temperature superconductors raised the question of whether such strong electron-phonon coupling is realized in cuprates. Strong coupling with some collective excitation mode has been indicated by a dispersion “kink”. However, there is intensive debate regarding whether the relevant coupling mode is a magnetic resonance mode or an oxygen buckling phonon mode. This ambiguity is a consequence of the energy of the main prominent kink. Here, we show a new landscape of dispersion kinks. We report that heavily overdoping a Bi2Sr2CaCu2O8+δ superconductor results in a decline of the conventional main kink and a rise of another sharp kink, along with substantial energy shifts of both. Notably, the latter kink can be ascribed only to an oxygen-breathing phonon. Hence, the multiple phonon branches provide a consistent account of our data set on the multiple kinks. Our results suggest that strong electron-phonon coupling and its dramatic change should be incorporated into or reconciled with scenarios for the evolution of high-Tc superconductivity.
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30
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Bi-2212/1T-TaS 2 Van der Waals junctions: Interplay of proximity induced high-T c superconductivity and CDW order. Sci Rep 2017; 7:4639. [PMID: 28680063 PMCID: PMC5498642 DOI: 10.1038/s41598-017-04645-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/17/2017] [Indexed: 11/12/2022] Open
Abstract
Understanding the coexistence, competition and/or cooperation between superconductivity and charge density waves (CDWs) in the transition metal dichalcogenides (TMDs) is an elusive goal which, when realized, promises to reveal fundamental information on this important class of materials. Here, we use four-terminal current-voltage measurements to study the Van der Waals interface between freshly exfoliated flakes of the high-Tc superconductor, Bi-2212, and the CDW-dominated TMD layered material, 1T-TaS2. For highly transparent barriers, there is a pronounced Andreev reflection feature providing evidence for proximity-induced high-Tc superconductivity in 1T-TaS2 with a surprisingly large energy gap (~20 meV) equal to half that of intrinsic Bi-2212 (~40 meV). Our systematic study using conductance spectroscopy of junctions with different transparencies also reveals the presence of two separate boson modes, each associated with a “dip-hump” structure. We infer that the proximity-induced high-Tc superconductivity in the 1T-TaS2 is driven by coupling to the metastable metallic phase coexisting within the Mott commensurate CDW (CCDW) phase and associated with a concomitant change of the CCDW order parameter in the interfacial region.
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31
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Imaging the real space structure of the spin fluctuations in an iron-based superconductor. Nat Commun 2017; 8:15996. [PMID: 28660875 PMCID: PMC5493767 DOI: 10.1038/ncomms15996] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Accepted: 05/17/2017] [Indexed: 11/19/2022] Open
Abstract
Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonance comes almost exclusively from neutron scattering. Here we demonstrate that by using low-temperature scanning tunnelling microscopy and spectroscopy we can characterize the spin resonance in real space. We show that inelastic tunnelling leads to the characteristic dip-hump feature seen in tunnelling spectra in high temperature superconductors and that this feature arises from excitations of the spin fluctuations. Spatial mapping of this feature near defects allows us to probe non-local properties of the spin susceptibility and to image its real space structure. The knowledge of how spin fluctuations affect high-Tc superconductivity comes exclusively from neutron scattering. Here, Chi et al. establish characteristic excitation features of the spin fluctuations in real space from the scanning tunnelling spectra in an iron-based superconductor.
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32
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Hlobil P, Jandke J, Wulfhekel W, Schmalian J. Tracing the Electronic Pairing Glue in Unconventional Superconductors via Inelastic Scanning Tunneling Spectroscopy. PHYSICAL REVIEW LETTERS 2017; 118:167001. [PMID: 28474901 DOI: 10.1103/physrevlett.118.167001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Indexed: 06/07/2023]
Abstract
Scanning tunneling microscopy has been shown to be a powerful experimental probe to detect electronic excitations and further allows us to deduce fingerprints of bosonic collective modes in superconductors. Here, we demonstrate that the inclusion of inelastic tunnel events is crucial for the interpretation of tunneling spectra of unconventional superconductors and allows us to directly probe electronic and bosonic excitations via scanning tunneling microscopy. We apply the formalism to the iron based superconductor LiFeAs. With the inclusion of inelastic contributions, we find strong evidence for a nonconventional pairing mechanism, likely via magnetic excitations.
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Affiliation(s)
- Patrik Hlobil
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76344 Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Jasmin Jandke
- Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
| | - Jörg Schmalian
- Institut für Festkörperphysik, Karlsruher Institut für Technologie, 76344 Karlsruhe, Germany
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131 Karlsruhe, Germany
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33
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Gozar A, Litombe NE, Hoffman JE, Božović I. Optical Nanoscopy of High T c Cuprate Nanoconstriction Devices Patterned by Helium Ion Beams. NANO LETTERS 2017; 17:1582-1586. [PMID: 28166407 DOI: 10.1021/acs.nanolett.6b04729] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Helium ion beams (HIB) focused to subnanometer scales have emerged as powerful tools for high-resolution imaging as well as nanoscale lithography, ion milling, or deposition. Quantifying irradiation effects is an essential step toward reliable device fabrication, but most of the depth profiling information is provided by computer simulations rather than the experiment. Here, we demonstrate the use of atomic force microscopy (AFM) combined with scanning near-field optical microscopy (SNOM) to provide three-dimensional (3D) dielectric characterization of high-temperature superconductor devices fabricated by HIB. By imaging the infrared dielectric response obtained from light demodulation at multiple harmonics of the AFM tapping frequency, we find that amorphization caused by the nominally 0.5 nm HIB extends throughout the entire 26.5 nm thickness of the cuprate film and by ∼500 nm laterally. This unexpectedly widespread damage in morphology and electronic structure can be attributed to a helium depth distribution substantially modified by the internal device interfaces. Our study introduces AFM-SNOM as a quantitative tomographic technique for noninvasive 3D characterization of irradiation damage in a wide variety of nanoscale devices.
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Affiliation(s)
- A Gozar
- Department of Applied Physics, Yale University , New Haven, Connecticut 06511, United States
- Energy Sciences Institute, Yale University , West Haven, Connecticut 06516, United States
| | - N E Litombe
- Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States
- Brookhaven National Laboratory , Upton, New York 11973, United States
| | - Jennifer E Hoffman
- Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States
| | - I Božović
- Department of Applied Physics, Yale University , New Haven, Connecticut 06511, United States
- Energy Sciences Institute, Yale University , West Haven, Connecticut 06516, United States
- Brookhaven National Laboratory , Upton, New York 11973, United States
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34
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Fanfarillo L, Mori M, Campetella M, Grilli M, Caprara S. Glue function of optimally and overdoped cuprates from inversion of the Raman spectra. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:065701. [PMID: 26790363 DOI: 10.1088/0953-8984/28/6/065701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We address the issue of identifying the mediators of effective interactions in cuprates superconductors. Specifically, we use inversion theory to analyze Raman spectra of optimally and over-doped La2-x Sr x CuO4 samples. This allows us to extract the so-called glue function without making any a priori assumption based on any specific model. We use instead two different techniques, namely the singular value decomposition and a multi-rectangle decomposition. With both techniques we find consistent results showing that: (i) two distinct excitations are responsible for the glue function, which have completely different doping dependence. One excitation becomes weak above optimal doping, where on the contrary the other keeps (or even slightly increases) its strength; (ii) there is a marked temperature dependence on the weight and spectral distribution of these excitations, which therefore must have a somewhat critical character. It is quite natural to identify and characterize these two distinct excitations as damped antiferromagnetic spin waves and damped charge density waves, respectively. This sets the stage for a scenario in which superconductivity is concomitant and competing with a charge ordering instability.
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Affiliation(s)
- L Fanfarillo
- Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, E-28049 Madrid, Spain
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35
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Jacobs T, Simsek Y, Koval Y, Müller P, Krasnov VM. Sequence of Quantum Phase Transitions in Bi2Sr2CaCu2O(8+δ) Cuprates Revealed by In Situ Electrical Doping of One and the Same Sample. PHYSICAL REVIEW LETTERS 2016; 116:067001. [PMID: 26919010 DOI: 10.1103/physrevlett.116.067001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Indexed: 06/05/2023]
Abstract
Our recently discovered electrical doping technique allows a broad-range variation of carrier concentration without changing the chemical composition. We show that it is possible to induce superconductivity in a nondoped insulating sample and to tune it reversibly all the way to an overdoped metallic state. This way, we can investigate the whole doping diagram of one and the same sample. Our study reveals two distinct critical points. The one at the overdoped side is associated with the onset of the pseudogap and with the metal-to-insulator transition in the c-axis transport. The other at optimal doping is associated with the appearance of a "dressed" electron energy. Our study confirms the existence of multiple phase transitions under the superconducting dome in cuprates.
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Affiliation(s)
- Th Jacobs
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
| | - Y Simsek
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
- Department of Physics, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
| | - Y Koval
- Department of Physics, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
| | - P Müller
- Department of Physics, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
| | - V M Krasnov
- Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
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36
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Li Y, Schaller RD, Zhu M, Walko DA, Kim J, Ke X, Miao L, Mao ZQ. Strong lattice correlation of non-equilibrium quasiparticles in a pseudospin-1/2 Mott insulator Sr2IrO4. Sci Rep 2016; 6:19302. [PMID: 26787094 PMCID: PMC4726248 DOI: 10.1038/srep19302] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 11/23/2015] [Indexed: 11/30/2022] Open
Abstract
In correlated oxides the coupling of quasiparticles to other degrees of freedom such as spin and lattice plays critical roles in the emergence of symmetry-breaking quantum ordered states such as high temperature superconductivity. We report a strong lattice coupling of photon-induced quasiparticles in spin-orbital coupling Mott insulator Sr2IrO4 probed via optical excitation. Combining time-resolved x-ray diffraction and optical spectroscopy techniques, we reconstruct a spatiotemporal map of the diffusion of these quasiparticles. Due to the unique electronic configuration of the quasiparticles, the strong lattice correlation is unexpected but extends the similarity between Sr2IrO4 and cuprates to a new dimension of electron-phonon coupling which persists under highly non-equilibrium conditions.
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Affiliation(s)
- Yuelin Li
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Richard D Schaller
- Center of Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Mengze Zhu
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
| | - Donald A Walko
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Xianglin Ke
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
| | - Ludi Miao
- Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, USA
| | - Z Q Mao
- Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, USA
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37
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Nanoscale determination of the mass enhancement factor in the lightly doped bulk insulator lead selenide. Nat Commun 2015; 6:6559. [PMID: 25814140 PMCID: PMC4389230 DOI: 10.1038/ncomms7559] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 02/09/2015] [Indexed: 11/16/2022] Open
Abstract
Bismuth chalcogenides and lead telluride/selenide alloys exhibit exceptional thermoelectric properties that could be harnessed for power generation and device applications. Since phonons play a significant role in achieving these desired properties, quantifying the interaction between phonons and electrons, which is encoded in the Eliashberg function of a material, is of immense importance. However, its precise extraction has in part been limited due to the lack of local experimental probes. Here we construct a method to directly extract the Eliashberg function using Landau level spectroscopy, and demonstrate its applicability to lightly doped thermoelectric bulk insulator PbSe. In addition to its high energy resolution only limited by thermal broadening, this novel experimental method could be used to detect variations in mass enhancement factor at the nanoscale level. This opens up a new pathway for investigating the local effects of doping and strain on the mass enhancement factor. Electron–phonon coupling influences the thermal and electronic properties of many solid materials. Zeljkovic et al. now combine Landau level spectroscopy and scanning tunnelling microscopy to extract quantitative information on electron–phonon coupling in the insulator lead selenide.
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38
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Hsiao J, Martyna GJ, Newns DM. Phase diagram of cuprate high-temperature superconductors described by a field theory based on anharmonic oxygen degrees of freedom. PHYSICAL REVIEW LETTERS 2015; 114:107001. [PMID: 25815959 DOI: 10.1103/physrevlett.114.107001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Indexed: 06/04/2023]
Abstract
In high temperature superconductors, although some phenomena such as the Mott transition (MT) at low doping are clearly driven by electron correlations, recent experimental data imply that anharmonic oxygen degrees of freedom-characteristic of perovskite materials-are playing a significant role. A key test of the role of anharmonic oxygen is to reproduce the complex cuprate phase diagram from a simple model. Here, we show that a field theory based on nonlinear coupling to anharmonic oxygens, parametrized from ab initio calculations, quantitatively reproduces the cuprate phase diagram for dopings above the MT. Pairing is mediated by renormalized oxygen vibrations transmuted into excitations of the pseudogap. The observed strong dependence of gap to transition temperature ratio on Tc also emerges from this field theory. This work suggests that including vibrational degrees of freedom is key to developing a complete understanding of the cuprates.
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Affiliation(s)
- Jenhao Hsiao
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Glenn J Martyna
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Dennis M Newns
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
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39
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Zeljkovic I, Nieminen J, Huang D, Chang TR, He Y, Jeng HT, Xu Z, Wen J, Gu G, Lin H, Markiewicz RS, Bansil A, Hoffman JE. Nanoscale interplay of strain and doping in a high-temperature superconductor. NANO LETTERS 2014; 14:6749-6753. [PMID: 25365704 DOI: 10.1021/nl501890k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The highest-temperature superconductors are electronically inhomogeneous at the nanoscale, suggesting the existence of a local variable that could be harnessed to enhance the superconducting pairing. Here we report the relationship between local doping and local strain in the cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+x). We use scanning tunneling microscopy to discover that the crucial oxygen dopants are periodically distributed in correlation with local strain. Our picoscale investigation of the intraunit-cell positions of all oxygen dopants provides essential structural input for a complete microscopic theory.
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Affiliation(s)
- Ilija Zeljkovic
- Department of Physics, Harvard University , Cambridge, Massachusetts 02138, United States
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40
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Song CL, Wang YL, Jiang YP, Li Z, Wang L, He K, Chen X, Hoffman JE, Ma XC, Xue QK. Imaging the electron-boson coupling in superconducting FeSe films using a scanning tunneling microscope. PHYSICAL REVIEW LETTERS 2014; 112:057002. [PMID: 24580624 DOI: 10.1103/physrevlett.112.057002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Indexed: 06/03/2023]
Abstract
Scanning tunneling spectroscopy has been used to reveal signatures of a bosonic mode in the local quasiparticle density of states of superconducting FeSe films. The mode appears below Tc as a "dip-hump" feature at energy Ω∼4.7kBTc beyond the superconducting gap Δ. Spectra on strained regions of the FeSe films reveal simultaneous decreases in Δ and Ω. This contrasts with all previous reports on other high-Tc superconductors, where Δ locally anticorrelates with Ω. A local strong coupling model is found to reconcile the discrepancy well, and to provide a unified picture of the electron-boson coupling in unconventional superconductors.
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Affiliation(s)
- Can-Li Song
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Yi-Lin Wang
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ye-Ping Jiang
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhi Li
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Lili Wang
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ke He
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xi Chen
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Jennifer E Hoffman
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Xu-Cun Ma
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qi-Kun Xue
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
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41
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Krasnov VM, Katterwe SO, Rydh A. Signatures of the electronic nature of pairing in high-T(c) superconductors obtained by non-equilibrium boson spectroscopy. Nat Commun 2013; 4:2970. [PMID: 24336159 PMCID: PMC3905708 DOI: 10.1038/ncomms3970] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/18/2013] [Indexed: 11/29/2022] Open
Abstract
Understanding the pairing mechanism that gives rise to high-temperature superconductivity is one of the longest-standing problems of condensed-matter physics. Almost three decades after its discovery, even the question of whether or not phonons are involved remains a point of contention to some. Here we describe a technique for determining the spectra of bosons generated during the formation of Cooper pairs on recombination of hot electrons as they tunnel between the layers of a cuprate superconductor. The results obtained indicate that the bosons that mediate pairing decay over micrometre-scale distances and picosecond timescales, implying that they propagate at a speed of around 106 m s−1. This value is more than two orders of magnitude greater than the phonon propagation speed but close to Fermi velocity for electrons, suggesting that the pairing mechanism is mediated by unconventional repulsive electron–electron, rather than attractive electron–phonon, interactions. The mechanism of high-temperature superconductivity remains a subject of debate. Krasnov et al. describe a technique for measuring the spectra of bosons generated during the formation of Cooper pairs in a cuprate, the results of which suggest that the process is governed by electron–electron interactions.
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Affiliation(s)
- Vladimir M Krasnov
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
| | - Sven-Olof Katterwe
- 1] Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden [2] Present address: Institut für Luft- und Kältetechnik gemeinnützige Gesellschaft mbH, Bertolt-Brecht-Allee 20, D-01309 Dresden, Germany
| | - Andreas Rydh
- Department of Physics, AlbaNova University Center, Stockholm University, SE-10691 Stockholm, Sweden
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42
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Alldredge JW, Calleja EM, Dai J, Eisaki H, Uchida S, McElroy K. The k-space origins of scattering in Bi2Sr2CaCu2O8+x. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:335601. [PMID: 23883664 DOI: 10.1088/0953-8984/25/33/335601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a general, computer automated procedure that inverts the reciprocal space scattering data (q-space) that are measured by spectroscopic imaging scanning tunnelling microscopy (SI-STM) in order to determine the momentum space (k-space) scattering structure. This allows a detailed examination of the k-space origins of the quasiparticle interference (QPI) pattern in Bi2Sr2CaCu2O8+x within the theoretical constraints of the joint density of states (JDOS). Our new method allows measurement of the differences between the positive and negative energy dispersions, the gap structure and an energy dependent scattering length scale. Furthermore, it resolves the transition between the dispersive QPI and the checkerboard ([Formula: see text] excitation). We have measured the k-space scattering structure over a wide range of doping (p ∼ 0.22-0.08), including regions where the octet model is not applicable. Our technique allows the complete mapping of the k-space scattering origins of the spatial excitations in Bi2Sr2CaCu2O8+x, which allows for better comparisons between SI-STM and other experimental probes of the band structure. By applying our new technique to such a heavily studied compound, we can validate our new general approach for determining the k-space scattering origins from SI-STM data.
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43
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Cilento F, Conte SD, Coslovich G, Banfi F, Ferrini G, Eisaki H, Greven M, Damascelli A, Marel DVD, Parmigiani F, Giannetti C. In search for the pairing glue in cuprates by non-equilibrium optical spectroscopy. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/449/1/012003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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44
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Gustafsson D, Golubev D, Fogelström M, Claeson T, Kubatkin S, Bauch T, Lombardi F. Fully gapped superconductivity in a nanometre-size YBa2Cu3O(7-δ) island enhanced by a magnetic field. NATURE NANOTECHNOLOGY 2013; 8:25-30. [PMID: 23223187 DOI: 10.1038/nnano.2012.214] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 11/06/2012] [Indexed: 06/01/2023]
Abstract
The symmetry of Cooper pairs is central to constructing a superconducting state. The demonstration of a d(x²-y²)-wave order parameter with nodes represented a breakthrough for high critical temperature superconductors (HTSs). However, despite this fundamental discovery, the origin of superconductivity remains elusive, raising the question of whether something is missing from the global picture. Deviations from d(x²-y²)-wave symmetry, such as an imaginary admixture d(x²-y²)+ is (or id(xy)), predict a ground state with unconventional properties exhibiting a full superconducting gap and time reversal symmetry breaking. The existence of such a state, until now highly controversial, can be proved by highly sensitive measurements of the excitation spectrum. Here, we present a spectroscopic technique based on an HTS nanoscale device that allows an unprecedented energy resolution thanks to Coulomb blockade effects, a regime practically inaccessible in these materials previously. We find that the energy required to add an extra electron depends on the parity (odd/even) of the excess electrons on the island and increases with magnetic field. This is inconsistent with a pure d(x²-y²)-wave symmetry and demonstrates a complex order parameter component that needs to be incorporated into any theoretical model of HTS.
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Affiliation(s)
- D Gustafsson
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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Derzsi M, Budzianowski A, Struzhkin VV, Malinowski PJ, Leszczyński PJ, Mazej Z, Grochala W. Redetermination of crystal structure of Ag(ii)SO4and its high-pressure behavior up to 30 GPa. CrystEngComm 2013. [DOI: 10.1039/c2ce26282g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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46
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Nowadnick EA, Johnston S, Moritz B, Scalettar RT, Devereaux TP. Competition between antiferromagnetic and charge-density-wave order in the half-filled Hubbard-Holstein model. PHYSICAL REVIEW LETTERS 2012; 109:246404. [PMID: 23368352 DOI: 10.1103/physrevlett.109.246404] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Indexed: 06/01/2023]
Abstract
We present a determinant quantum Monte Carlo study of the competition between instantaneous on-site Coulomb repulsion and retarded phonon-mediated attraction between electrons, as described by the two-dimensional Hubbard-Holstein model. At half filling, we find a strong competition between antiferromagnetism (AFM) and charge-density-wave (CDW) order. We demonstrate that a simple picture of AFM-CDW competition that incorporates the phonon-mediated attraction into an effective-U Hubbard model requires significant refinement. Specifically, retardation effects slow the onset of charge order so that CDW order remains absent even when the effective U is negative. This delay opens a window where neither AFM nor CDW order is well established and where there are signatures of a possible metallic phase.
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Affiliation(s)
- E A Nowadnick
- Department of Physics, Stanford University, Stanford, California 94305, USA
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Chi S, Grothe S, Liang R, Dosanjh P, Hardy WN, Burke SA, Bonn DA, Pennec Y. Scanning tunneling spectroscopy of superconducting LiFeAs single crystals: evidence for two nodeless energy gaps and coupling to a bosonic mode. PHYSICAL REVIEW LETTERS 2012; 109:087002. [PMID: 23002767 DOI: 10.1103/physrevlett.109.087002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Indexed: 06/01/2023]
Abstract
The superconducting compound LiFeAs is studied by scanning tunneling microscopy and spectroscopy. A gap map of the unreconstructed surface indicates a high degree of homogeneity in this system. Spectra at 2 K show two nodeless superconducting gaps with Δ(1)=5.3±0.1 meV and Δ(2)=2.5±0.2 meV. The gaps close as the temperature is increased to the bulk T(c), indicating that the surface accurately represents the bulk. A dip-hump structure is observed below T(c) with an energy scale consistent with a magnetic resonance recently reported by inelastic neutron scattering.
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Affiliation(s)
- Shun Chi
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
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Shan L, Gong J, Wang YL, Shen B, Hou X, Ren C, Li C, Yang H, Wen HH, Li S, Dai P. Evidence of a spin resonance mode in the iron-based superconductor Ba(0.6)K(0.4)Fe2As2 from scanning tunneling spectroscopy. PHYSICAL REVIEW LETTERS 2012; 108:227002. [PMID: 23003642 DOI: 10.1103/physrevlett.108.227002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Indexed: 06/01/2023]
Abstract
We used high-resolution scanning tunneling spectroscopy to study the hole-doped iron pnictide superconductor Ba(0.6)K(0.4)Fe(2)As(2) (T(c)=38 K). Features of a bosonic excitation (mode) are observed in the measured quasiparticle density of states. The bosonic features are intimately associated with the superconducting order parameter and have a mode energy of ~14 meV, similar to the spin resonance measured by inelastic neutron scattering. These results indicate a strong electron-spin excitation coupling in iron pnictide superconductors, similar to that in high-T(c) copper oxide superconductors.
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Affiliation(s)
- Lei Shan
- National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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Dal Conte S, Giannetti C, Coslovich G, Cilento F, Bossini D, Abebaw T, Banfi F, Ferrini G, Eisaki H, Greven M, Damascelli A, van der Marel D, Parmigiani F. Disentangling the electronic and phononic glue in a high-Tc superconductor. Science 2012; 335:1600-3. [PMID: 22461606 DOI: 10.1126/science.1216765] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Unveiling the nature of the bosonic excitations that mediate the formation of Cooper pairs is a key issue for understanding unconventional superconductivity. A fundamental step toward this goal would be to identify the relative weight of the electronic and phononic contributions to the overall frequency (Ω)-dependent bosonic function, Π(Ω). We performed optical spectroscopy on Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+δ) crystals with simultaneous time and frequency resolution; this technique allowed us to disentangle the electronic and phononic contributions by their different temporal evolution. The spectral distribution of the electronic excitations and the strength of their interaction with fermionic quasiparticles fully account for the high critical temperature of the superconducting phase transition.
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Affiliation(s)
- S Dal Conte
- Department of Physics A. Volta, Università degli Studi di Pavia, Pavia, Italy
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d-Wave Superconductivity and s-Wave Charge Density Waves: Coexistence between Order Parameters of Different Origin and Symmetry. Symmetry (Basel) 2011. [DOI: 10.3390/sym3040699] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A review of the theory describing the coexistence between d-wave superconductivity and s-wave charge-density-waves (CDWs) is presented. The CDW gapping is identified with pseudogapping observed in high-Tc oxides. According to the cuprate specificity, the analysis is carried out for the two-dimensional geometry of the Fermi surface (FS). Phase diagrams on the σ0 − α plane—here, σ0 is the ratio between the energy gaps in the parent pure CDW and superconducting states, and the quantity 2α is connected with the degree of dielectric (CDW) FS gapping—were obtained for various possible configurations of the order parameters in the momentum space. Relevant tunnel and photoemission experimental data for high-Tc oxides are compared with theoretical predictions. A brief review of the results obtained earlier for the coexistence between s-wave superconductivity and CDWs is also given.
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