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Johnsen LG. The magnetic field driven superconductor-metal transition in disordered hole-overdoped cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:115601. [PMID: 36580677 DOI: 10.1088/1361-648x/acaf1e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 12/29/2022] [Indexed: 06/17/2023]
Abstract
By solving the Bogoliubov-de Gennes equations for ad-wave superconductor, we explore how the interplay between disorder and the orbital depairing of an external magnetic field influences the superconductor-metal transition of the hole-overdoped cuprates. For highly disordered systems, we find granular Cooper paring to persist above the critical field where the superfluid stiffness goes to zero. We also show that because the vortices are attracted to regions where the superconducting pairing is already weak, the Caroli-de Gennes-Matricon zero-bias peak in the local density of states at the vortex cores disappears already at moderate disorder.
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Affiliation(s)
- Lina G Johnsen
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
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2
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Abstract
A translation-invariant (TI) bipolaron theory of superconductivity based, like Bardeen–Cooper–Schrieffer theory, on Fröhlich Hamiltonian is presented. Here the role of Cooper pairs belongs to TI bipolarons which are pairs of spatially delocalized electrons whose correlation length of a coupled state is small. The presence of Fermi surface leads to the stabilization of such states in its vicinity and a possibility of their Bose–Einstein condensation (BEC). The theory provides a natural explanation of the existence of a pseudogap phase preceding the superconductivity and enables one to estimate the temperature of a transition T * from a normal state to a pseudogap one. It is shown that the temperature of BEC of TI bipolarons determines the temperature of a superconducting transition T c which depends not on the bipolaron effective mass but on the ordinary mass of a band electron. This removes restrictions on the upper limit of T c for a strong electron-phonon interaction. A natural explanation is provided for the angular dependence of the superconducting gap which is determined by the angular dependence of the phonon spectrum. It is demonstrated that a lot of experiments on thermodynamic and transport characteristics, Josephson tunneling and angle-resolved photoemission spectroscopy (ARPES) of high-temperature superconductors does not contradict the concept of a TI bipolaron mechanism of superconductivity in these materials. Possible ways of enhancing T c and producing new room-temperature superconductors are discussed on the basis of the theory suggested.
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3
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Relation of Superconducting Pairing Symmetry and Non-Magnetic Impurity Effects in Vortex States. Symmetry (Basel) 2020. [DOI: 10.3390/sym12010175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Non-magnetic impurity scattering effects on the vortex core states are theoretically studied to clarify the contributions from the sign-change of the pairing function in anisotropic superconductors. The vortex states are calculated by the Eilenberger theory in superconductors with p x -wave pairing symmetry, as well as the corresponding anisotropic s-wave symmetry. From the spatial structure of the pair potential and the local electronic states around a vortex, we examine the differences between anisotropic superconductors with and without sign-change of the pairing function, and estimate how twofold symmetric vortex core images change with increasing the impurity scattering rate both in the Born and the unitary limits. We found that twofold symmetric vortex core image of zero-energy local density of states changes the orientation of the twofold symmetry with increasing the scattering rate when the sign change occurs in the pairing function. Without the sign change, the vortex core shape reduces to circular one with approaching dirty cases. These results of the impurity effects are valuable for identifying the pairing symmetry by observation of the vortex core image by the STM observation.
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4
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Zhao SYF, Poccia N, Panetta MG, Yu C, Johnson JW, Yoo H, Zhong R, Gu GD, Watanabe K, Taniguchi T, Postolova SV, Vinokur VM, Kim P. Sign-Reversing Hall Effect in Atomically Thin High-Temperature Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} Superconductors. PHYSICAL REVIEW LETTERS 2019; 122:247001. [PMID: 31322397 DOI: 10.1103/physrevlett.122.247001] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Revised: 01/31/2019] [Indexed: 06/10/2023]
Abstract
We developed novel techniques to fabricate atomically thin Bi_{2.1}Sr_{1.9}CaCu_{2.0}O_{8+δ} van der Waals heterostructures down to two unit cells while maintaining a transition temperature T_{c} close to the bulk, and carry out magnetotransport measurements on these van der Waals devices. We find a double sign change of the Hall resistance R_{xy} as in the bulk system, spanning both below and above T_{c}. Further, we observe a drastic enlargement of the region of sign reversal in the temperature-magnetic field phase diagram with decreasing thickness of the device. We obtain quantitative agreement between experimental R_{xy}(T,B) and the predictions of the vortex dynamics-based description of Hall effect in high-temperature superconductors both above and below T_{c}.
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Affiliation(s)
- S Y Frank Zhao
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Nicola Poccia
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Margaret G Panetta
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Cyndia Yu
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Jedediah W Johnson
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Hyobin Yoo
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Ruidan Zhong
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - G D Gu
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
| | - Svetlana V Postolova
- Institute for Physics of Microstructures RAS, Nizhny Novgorod 603950, Russia
- Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090, Russia
| | - Valerii M Vinokur
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Consortium for Advanced Science and Engineering, Office of Research and National Laboratories, University of Chicago, Chicago, Illinois 60637, USA
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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5
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Chen M, Chen X, Yang H, Du Z, Zhu X, Wang E, Wen HH. Discrete energy levels of Caroli-de Gennes-Matricon states in quantum limit in FeTe 0.55Se 0.45. Nat Commun 2018; 9:970. [PMID: 29511191 PMCID: PMC5840178 DOI: 10.1038/s41467-018-03404-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/11/2018] [Indexed: 11/13/2022] Open
Abstract
Caroli-de Gennes-Matricon (CdGM) states were predicted in 1964 as low-energy excitations within vortex cores of type-II superconductors. In the quantum limit, the energy levels of these states were predicted to be discrete with the basic levels at ±μΔ2/EF (μ = 1/2, 3/2, 5/2, …) with Δ the superconducting energy gap and EF the Fermi energy. However, due to the small ratio of Δ/EF in most type-II superconductors, it is very difficult to observe the discrete CdGM states, but rather a symmetric peak which appears at zero bias at the vortex center. Here we report the clear observation of these discrete energy levels of CdGM states in FeTe0.55Se0.45. The rather stable energies of these bound state peaks vs. space clearly validate our conclusion. Analysis based on the energies of these CdGM states indicates that the Fermi energy in the present system is very small.
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Affiliation(s)
- Mingyang Chen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Xiaoyu Chen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Huan Yang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
| | - Zengyi Du
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Xiyu Zhu
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Enyu Wang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China
| | - Hai-Hu Wen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center for Advanced Microstructures, Nanjing University, 210093, Nanjing, China.
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6
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Gyenis A, Feldman BE, Randeria MT, Peterson GA, Bauer ED, Aynajian P, Yazdani A. Visualizing heavy fermion confinement and Pauli-limited superconductivity in layered CeCoIn 5. Nat Commun 2018; 9:549. [PMID: 29416021 PMCID: PMC5803268 DOI: 10.1038/s41467-018-02841-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 01/03/2018] [Indexed: 11/09/2022] Open
Abstract
Layered material structures play a key role in enhancing electron–electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of bulk properties. Here we use scanning tunneling microscopy to directly probe in cross-section the quasi-two-dimensional electronic states of the heavy fermion superconductor CeCoIn5. Our measurements reveal the strong confined nature of quasiparticles, anisotropy of tunneling characteristics, and layer-by-layer modulated behavior of the precursor pseudogap gap phase. In the interlayer coupled superconducting state, the orientation of line defects relative to the d-wave order parameter determines whether in-gap states form due to scattering. Spectroscopic imaging of the anisotropic magnetic vortex cores directly characterizes the short interlayer superconducting coherence length and shows an electronic phase separation near the upper critical in-plane magnetic field, consistent with a Pauli-limited first-order phase transition into a pseudogap phase. The electronic properties along the out-of-plane direction of layered materials are often inferred indirectly. Here, Gyenis et al. directly probe in cross-section the quasi-two-dimensional correlated electronic states of the heavy fermion superconductor CeCoIn5.
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Affiliation(s)
- András Gyenis
- Joseph Henry Laboratories of Physics, Department of Physics, Princeton University, Princeton, NJ, 08544, USA.,Department of Electrical Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Benjamin E Feldman
- Joseph Henry Laboratories of Physics, Department of Physics, Princeton University, Princeton, NJ, 08544, USA.,Department of Physics, Stanford University, Stanford, CA, 94305, USA
| | - Mallika T Randeria
- Joseph Henry Laboratories of Physics, Department of Physics, Princeton University, Princeton, NJ, 08544, USA
| | - Gabriel A Peterson
- Joseph Henry Laboratories of Physics, Department of Physics, Princeton University, Princeton, NJ, 08544, USA.,National Institute of Standards and Technology, Boulder, CO, 80305, USA
| | - Eric D Bauer
- Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Pegor Aynajian
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, NY, 13902, USA
| | - Ali Yazdani
- Joseph Henry Laboratories of Physics, Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
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7
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Stock C, Rodriguez EE, Lee N, Demmel F, Fouquet P, Laver M, Niedermayer C, Su Y, Nemkovski K, Green MA, Rodriguez-Rivera JA, Kim JW, Zhang L, Cheong SW. Orphan Spins in the S=5/2 Antiferromagnet CaFe_{2}O_{4}. PHYSICAL REVIEW LETTERS 2017; 119:257204. [PMID: 29303328 DOI: 10.1103/physrevlett.119.257204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Indexed: 06/07/2023]
Abstract
CaFe_{2}O_{4} is an anisotropic S=5/2 antiferromagnet with two competing A (↑↑↓↓) and B (↑↓↑↓) magnetic order parameters separated by static antiphase boundaries at low temperatures. Neutron diffraction and bulk susceptibility measurements, show that the spins near these boundaries are weakly correlated and a carry an uncompensated ferromagnetic moment that can be tuned with a magnetic field. Spectroscopic measurements find these spins are bound with excitation energies less than the bulk magnetic spin waves and resemble the spectra from isolated spin clusters. Localized bound orphaned spins separate the two competing magnetic order parameters in CaFe_{2}O_{4}.
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Affiliation(s)
- C Stock
- School of Physics and Astronomy and Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - E E Rodriguez
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
| | - N Lee
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
| | - F Demmel
- ISIS Facility, Rutherford Appleton Labs, Chilton, Didcot OX11 0QX, United Kingdom
| | - P Fouquet
- Institute Laue-Langevin, 6 rue Jules Horowitz, Boite Postale 156, 38042 Grenoble Cedex 9, France
| | - M Laver
- School of Metallurgy and Materials, University of Birmingham, B15 2TT, United Kingdom
| | - Ch Niedermayer
- Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - Y Su
- Jülich Centre for Neuton Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - K Nemkovski
- Jülich Centre for Neuton Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, D-85747 Garching, Germany
| | - M A Green
- School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J A Rodriguez-Rivera
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
- Department of Materials Science, University of Maryland, College Park, Maryland 20742, USA
| | - J W Kim
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
| | - L Zhang
- Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - S-W Cheong
- Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
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8
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Berthod C, Maggio-Aprile I, Bruér J, Erb A, Renner C. Observation of Caroli-de Gennes-Matricon Vortex States in YBa_{2}Cu_{3}O_{7-δ}. PHYSICAL REVIEW LETTERS 2017; 119:237001. [PMID: 29286696 DOI: 10.1103/physrevlett.119.237001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 06/07/2023]
Abstract
The copper oxides present the highest superconducting temperature and properties at odds with other compounds, suggestive of a fundamentally different superconductivity. In particular, the Abrikosov vortices fail to exhibit localized states expected and observed in all clean superconductors. We have explored the possibility that the elusive vortex-core signatures are actually present but weak. Combining local tunneling measurements with large-scale theoretical modeling, we positively identify the vortex states in YBa_{2}Cu_{3}O_{7-δ}. We explain their spectrum and the observed variations thereof from one vortex to the next by considering the effects of nearby vortices and disorder in the vortex lattice. We argue that the superconductivity of copper oxides is conventional, but the spectroscopic signature does not look so because the superconducting carriers are a minority.
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Affiliation(s)
- Christophe Berthod
- Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Ivan Maggio-Aprile
- Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Jens Bruér
- Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva, Switzerland
| | - Andreas Erb
- Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-Meissner-Strasse 8, D-85748 Garching, Germany
| | - Christoph Renner
- Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva, Switzerland
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9
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Sacks W, Mauger A, Noat Y. Universal spectral signatures in pnictides and cuprates: the role of quasiparticle-pair coupling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:445601. [PMID: 28837054 DOI: 10.1088/1361-648x/aa884a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the physical properties of a large variety of high-T c superconductors (SC), the cuprate family as well as the more recent iron-based superconductors, is still a major challenge. In particular, these materials exhibit the 'peak-dip-hump' structure in the quasiparticle density of states (DOS). The origin of this structure is explained within our pair-pair interaction (PPI) model: The non-superconducting state consists of incoherent pairs, a 'Cooper-pair glass' which, due to the PPI, undergoes a Bose-like condensation below T c to the coherent SC state. We derive the equations of motion for the quasiparticle operators showing that the DOS 'peak-dip-hump' is caused by the coupling between quasiparticles and excited pair states, or 'super-quasiparticles'. The renormalized SC gap function becomes energy-dependent and non retarded, reproducing accurately the experimental spectra of both pnictides and cuprates, despite the large difference in gap value.
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Affiliation(s)
- William Sacks
- Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), UMR 7590, Sorbonne Universités, UPMC Paris 6, 4 place Jussieu, 75252 Paris Cedex 05, France
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10
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Bipartite electronic superstructures in the vortex core of Bi2Sr2CaCu2O8+δ. Nat Commun 2016; 7:11747. [PMID: 27230420 PMCID: PMC4895017 DOI: 10.1038/ncomms11747] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 04/22/2016] [Indexed: 12/02/2022] Open
Abstract
The central issue in the physics of cuprate superconductivity is the mutual relationship among superconductivity, pseudogap and broken-spatial-symmetry states. A magnetic field B suppresses superconductivity, providing an opportunity to investigate the competition among these states. Although various B-induced electronic superstructures have been reported, their energy, spatial and momentum-space structures are unclear. Here, we show using spectroscopic-imaging scanning tunnelling microscopy on Bi2Sr2CaCu2O8+δ that there are two distinct B-induced electronic superstructures, both being localized in the vortex core but appearing at different energies. In the low-energy range where the nodal Bogoliubov quasiparticles are well-defined, we observe the so-called vortex checkerboard that we identify as the B-enhanced quasiparticle interference pattern. By contrast, in the high-energy region where the pseudogap develops, the broken-spatial-symmetry patterns that pre-exist at B=0 T is locally enhanced in the vortex core. This evidences the competition between superconductivity and the broken-spatial-symmetry state that is associated with the pseudogap. Field-induced electronic structures with spatial, momentum and energy resolution reveal the nature of interaction among multiple phases in correlated materials. Here, Machida et al. report two magnetic field-induced electronic superstructures in Bi2Se2CaCu2O8+δ, evidencing competition between superconductivity and emerging states.
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11
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Anisotropic superconducting gap and elongated vortices with Caroli-De Gennes-Matricon states in the new superconductor Ta4Pd3Te16. Sci Rep 2015; 5:9408. [PMID: 25797138 PMCID: PMC4369749 DOI: 10.1038/srep09408] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 03/02/2015] [Indexed: 11/17/2022] Open
Abstract
The superconducting state is formed by the condensation of a large number of Cooper pairs. The normal state electronic properties can give significant influence on the superconducting state. For usual type-II superconductors, the vortices are cylinder like with a round cross-section. For many two dimensional superconductors, such as Cuprates, albeit the in-plane anisotropy, the vortices generally have a round shape. In this paper we report results based on the scanning tunnelling microscopy/spectroscopy measurements on a newly discovered superconductor Ta4Pd3Te16. The chain-like conducting channels of PdTe2 in Ta4Pd3Te16 make a significant anisotropy of the in-plane Fermi velocity. We suggest at least one anisotropic superconducting gap with gap minima or possible node exists in this multiband system. In addition, elongated vortices are observed with an anisotropy of ξ||b/ξ&bottom⊥b ≈ 2.5. Clear Caroli-de Gennes-Matricon states are also observed within the vortex cores. Our results will initiate the study on the elongated vortices and superconducting mechanism in the new superconductor Ta4Pd3Te16.
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12
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Kopnin NB, Khaymovich IM, Mel'nikov AS. Predicted multiple cores of a magnetic vortex threading a two-dimensional metal proximity coupled to a superconductor. PHYSICAL REVIEW LETTERS 2013; 110:027003. [PMID: 23383934 DOI: 10.1103/physrevlett.110.027003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Indexed: 06/01/2023]
Abstract
The structure of a proximity induced vortex core in a two-dimensional metallic layer covering a superconducting half-space is calculated. We predict the formation of a multiple vortex core characterized by two-scale behavior of the local density of states. For coherent tunneling between the two-dimensional layer and the bulk superconductor, the spectrum has two subgap branches while for incoherent tunneling only one of them remains. The resulting splitting of the zero-bias anomaly and the multiple peak structure in the local density of states should be visible in the tunneling spectroscopy experiments.
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Affiliation(s)
- N B Kopnin
- O. V. Lounasmaa Laboratory, Aalto University, P.O. Box 15100, 00076 Aalto, Finland
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13
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Zeljkovic I, Hoffman JE. Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors. Phys Chem Chem Phys 2013; 15:13462-78. [DOI: 10.1039/c3cp51387d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Zeljkovic I, Xu Z, Wen J, Gu G, Markiewicz RS, Hoffman JE. Imaging the Impact of Single Oxygen Atoms on Superconducting Bi2+ySr2-yCaCu2O8+x. Science 2012; 337:320-3. [PMID: 22822144 DOI: 10.1126/science.1218648] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Ilija Zeljkovic
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
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15
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Beanland J, Alexandrov AS. Theory of extrinsic and intrinsic tunnelling in cuprate superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:403202. [PMID: 21386561 DOI: 10.1088/0953-8984/22/40/403202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
There has been a huge theoretical and experimental push to try to illuminate the mechanism behind the high-temperature superconductivity of copper oxides. Cuprates are distinguishable from conventional metallic superconductors in originating from the doping of the parent charge-transfer insulators. The superconducting parts are weakly coupled two-dimensional doped layers held together by the parent lattice. Apart from their high-T(c) they have other characteristic features including the 'superconducting' gap (SG) which develops below the superconducting critical temperature and can be seen in extrinsic and intrinsic tunnelling experiments as well as using high-resolution angle-resolved photoemission (ARPES); there also exists another energy gap, the 'pseudogap' (PG), which is a large anomalous gap that exists well above T(c). We present a brief review of recent theories behind the pseudogap and discuss in detail one specific (polaronic) approach which explains the SG, PG and unusual tunnelling characteristics of cuprate superconductors.
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Affiliation(s)
- J Beanland
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK
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16
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Ning YX, Song CL, Wang YL, Chen X, Jia JF, Xue QK, Ma XC. Vortex properties of two-dimensional superconducting Pb films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:065701. [PMID: 21389372 DOI: 10.1088/0953-8984/22/6/065701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Using low temperature scanning tunnelling microscopy/spectroscopy (STM/STS) we have investigated the vortex behaviours of two-dimensional superconducting Pb films at different thicknesses. STS at the vortex core shows an evolution of electronic states with film thickness. Transition from the clean limit to the dirty limit of superconductivity is identified, which can be ascribed to the decreased electronic mean free path induced by stronger scattering from the disordered interface at smaller thicknesses. A magnetic field dependent vortex core size is observed even for such a low- κ superconductor. The weak pinning induced by surface defects leads to the formation of a distorted hexagonal vortex lattice.
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Affiliation(s)
- Y X Ning
- Institute of Physics, The Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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17
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Alexandrov AS, Beanland J. Superconducting gap, normal state pseudogap, and tunneling spectra of bosonic and cuprate superconductors. PHYSICAL REVIEW LETTERS 2010; 104:026401. [PMID: 20366612 DOI: 10.1103/physrevlett.104.026401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Indexed: 05/29/2023]
Abstract
We develop a theory of normal metal-superconductor and superconductor tunneling in "bosonic" superconductors with strong attractive correlations taking into account coherence effects in single-particle excitation spectrum and disorder. The theory accounts for the existence of two energy scales, their temperature and doping dependencies, asymmetry, and inhomogeneity of tunneling spectra of underdoped cuprate superconductors.
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Affiliation(s)
- A S Alexandrov
- Department of Physics, Loughborough University, Loughborough LE11 3TU, United Kingdom
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18
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Yin Y, Zech M, Williams TL, Wang XF, Wu G, Chen XH, Hoffman JE. Scanning tunneling spectroscopy and vortex imaging in the iron pnictide superconductor BaFe1.8Co0.2As2. PHYSICAL REVIEW LETTERS 2009; 102:097002. [PMID: 19392555 DOI: 10.1103/physrevlett.102.097002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Indexed: 05/27/2023]
Abstract
We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe1.8Co0.2As2 single crystals in magnetic fields up to 9 T. At zero field, a single gap with coherence peaks at Delta=6.25 meV is observed in the density of states. At 9 and 6 T, we image a disordered vortex lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with strong-scattering surface impurities, demonstrating bulk pinning. The vortex-induced subgap density of states fits an exponential decay from the vortex center, from which we extract a coherence length xi=27.6+/-2.9 A, corresponding to an upper critical field Hc2=43 T.
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Affiliation(s)
- Yi Yin
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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19
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Kohen A, Proslier T, Cren T, Noat Y, Sacks W, Berger H, Roditchev D. Probing the superfluid velocity with a superconducting tip: the Doppler shift effect. PHYSICAL REVIEW LETTERS 2006; 97:027001. [PMID: 16907476 DOI: 10.1103/physrevlett.97.027001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Indexed: 05/11/2023]
Abstract
We address the question of probing the supercurrents in superconducting (SC) samples on a local scale by performing scanning tunneling spectroscopy (STS) experiments with a SC tip. In this configuration, we show that the tunneling conductance is highly sensitive to the Doppler shift term in the SC quasiparticle (QP) spectrum of the sample, thus allowing the local study of the superfluid velocity. Intrinsic screening currents, such as those surrounding the vortex cores in a type II SC in a magnetic field, are directly probed. With Nb tips, the STS mapping of the vortices, in single crystal 2H-NbSe(2), reveals both the vortex cores, on the scale of the SC coherence length xi, and the supercurrents, on the scale of the London penetration length lambda. A subtle interplay between the SC pair potential and the supercurrents at the vortex edge is observed. Our results open interesting prospects for the study of screening currents in any superconductor.
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Affiliation(s)
- A Kohen
- Institut des Nanosciences de Paris, I.N.S.P., Universités Paris 6 et 7, C.N.R.S., UMR 75 88, 75015 Paris, France
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20
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Ouazi S, Bobroff J, Alloul H, Le Tacon M, Blanchard N, Collin G, Julien MH, Horvatić M, Berthier C. Impurity-induced local magnetism and density of states in the superconducting state of YBa2Cu3O7. PHYSICAL REVIEW LETTERS 2006; 96:127005. [PMID: 16605949 DOI: 10.1103/physrevlett.96.127005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2005] [Indexed: 05/08/2023]
Abstract
17O NMR is used to probe the local influence of nonmagnetic Zn and magnetic Ni impurities in the superconducting state of optimally doped high TC YBa2Cu3O7. Zn and Ni induce a staggered paramagnetic polarization, similar to that evidenced above TC, with a typical extension xi=3 cell units for Zn and xi>or=3 for Ni. In addition, Zn is observed to induce a local density of states near the Fermi energy in its neighborhood, which also decays over about 3 cell units. Its magnitude decreases sharply with increasing temperature. This allows direct comparison with the STM observations done in BiSCCO.
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Affiliation(s)
- S Ouazi
- Laboratoire de Physique des Solides, UMR8502, Université Paris XI, 91405 Orsay, France
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21
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Sacépé B, Chapelier C, Marcenat C, Kacmarcik J, Klein T, Bernard M, Bustarret E. Tunneling spectroscopy and vortex imaging in boron-doped diamond. PHYSICAL REVIEW LETTERS 2006; 96:097006. [PMID: 16606302 DOI: 10.1103/physrevlett.96.097006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Indexed: 05/08/2023]
Abstract
We present the first scanning tunneling spectroscopy study of single-crystalline boron-doped diamond. The measurements were performed below 100 mK with a low temperature scanning tunneling microscope. The tunneling density of states displays a clear superconducting gap. The temperature evolution of the order parameter follows the weak-coupling BCS law with Delta(0)/kBTc approximately 1.74. Vortex imaging at low magnetic field also reveals localized states inside the vortex core that are unexpected for such a dirty superconductor.
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Affiliation(s)
- B Sacépé
- DRFMC-SPSMS, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
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22
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McElroy K, Gweon GH, Zhou SY, Graf J, Uchida S, Eisaki H, Takagi H, Sasagawa T, Lee DH, Lanzara A. Elastic scattering susceptibility of the high temperature superconductor Bi2Sr2CaCu2O(8+delta): a comparison between real and momentum space photoemission spectroscopies. PHYSICAL REVIEW LETTERS 2006; 96:067005. [PMID: 16606036 DOI: 10.1103/physrevlett.96.067005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Indexed: 05/08/2023]
Abstract
The joint density of states of Bi2Sr2CaCu2O(8+delta) is calculated by evaluating the autocorrelation of the single particle spectral function A(k, omega) measured from angle resolved photoemission spectroscopy (ARPES). These results are compared with Fourier transformed (FT) conductance modulations measured by scanning tunneling microscopy (STM). Good agreement between the two experimental probes is found for two different doping values examined. In addition, by comparing the FT-STM results to the autocorrelated ARPES spectra with different photon polarization, new insight on the form of the STM matrix elements is obtained. This shines new light on unsolved mysteries in the tunneling data.
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Affiliation(s)
- K McElroy
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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23
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Levy G, Kugler M, Manuel AA, Fischer O, Li M. Fourfold structure of vortex-core states in Bi2Sr2CaCu2O8+delta. PHYSICAL REVIEW LETTERS 2005; 95:257005. [PMID: 16384499 DOI: 10.1103/physrevlett.95.257005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Revised: 08/04/2005] [Indexed: 05/05/2023]
Abstract
We present a detailed study of vortex-core spectroscopy in slightly overdoped Bi2Sr2CaCu2O8+delta using a low-temperature scanning tunneling microscope. Inside the vortex core, we observe a fourfold symmetric modulation of the local density of states with an energy-independent period of (4.3 +/- 0.3)a0. Furthermore, we demonstrate that this square modulation is related to the vortex-core states which are located at +/-6 meV. Since the core-state energy is proportional to the superconducting gap magnitude , our results strongly suggest the existence of a direct relation between the superconducting state and the local electronic modulations in the vortex core.
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Affiliation(s)
- Giorgio Levy
- DPMC, Université de Genève, 24 Quai Ernest-Ansermet, CH-1211 Genève 4, Switzerland.
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24
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Honerkamp C, Lee PA. Staggered flux vortices and the superconducting transition in the layered cuprates. PHYSICAL REVIEW LETTERS 2004; 92:177002. [PMID: 15169183 DOI: 10.1103/physrevlett.92.177002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Indexed: 05/24/2023]
Abstract
We propose an effective model for the superconducting transition in the high-T(c) cuprates motivated by the SU(2) gauge theory approach. In addition to variations of the superconducting phase we allow for local admixture of staggered flux order. This leads to an unbinding transition of vortices with a staggered flux core that are energetically preferable to conventional vortices. Based on parameter estimates for the two-dimensional t-J model we argue that the staggered flux vortices provide a way to understand a phase with a moderate density of mobile vortices over a large temperature range above T(c) that yet exhibits otherwise normal transport properties. This picture is consistent with the large Nernst signal observed in this region.
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Affiliation(s)
- Carsten Honerkamp
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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25
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Howald C, Eisaki H, Kaneko N, Kapitulnik A. Coexistence of periodic modulation of quasiparticle states and superconductivity in Bi2Sr2CaCu2O8+delta. Proc Natl Acad Sci U S A 2003; 100:9705-9. [PMID: 12913127 PMCID: PMC187829 DOI: 10.1073/pnas.1233768100] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this article we show, using scanning tunneling spectroscopy, the existence of static striped density of electronic states in nearly optimally doped Bi2Sr2CaCu2O8+delta in zero field. This modulation is aligned with the Cu-O bonds, with a periodicity of four lattice constants, and exhibits features characteristic of a two-dimensional system of line objects. We further show that the density of states modulation manifests itself as a shift of states from above to below the superconducting gap. The fact that a single energy scale (i.e., the gap) appears for both superconductivity and stripes suggests that these two effects have the same origin.
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Affiliation(s)
- C Howald
- Department of Physics, Stanford University, Stanford, CA 94305, USA
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26
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Kakuyanagi K, Kumagai K, Matsuda Y, Hasegawa M. Antiferromagnetic vortex core in Tl(2)Ba(2)CuO(6+delta) studied by nuclear magnetic resonance. PHYSICAL REVIEW LETTERS 2003; 90:197003. [PMID: 12785974 DOI: 10.1103/physrevlett.90.197003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2002] [Indexed: 05/24/2023]
Abstract
Spatially resolved NMR is used to probe the magnetism in and around vortex cores of nearly optimally doped Tl(2)Ba(2)CuO(6+delta) (T(c)=85 K). The NMR relaxation rate T(-1)1 at the 205Tl site provides direct evidence that the antiferromagnetic (AF) spin correlation is significantly enhanced in the vortex core region. In the core region Cu spins show a local AF ordering with moments parallel to the layers at T(N)=20 K. Above T(N) the core region is in the paramagnetic state which is a reminiscence of the state above the pseudogap temperature (T(*) approximately 120 K), indicating that the pseudogap disappears within cores.
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Affiliation(s)
- K Kakuyanagi
- Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
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27
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Wang Y, Ono S, Onose Y, Gu G, Ando Y, Tokura Y, Uchida S, Ong NP. Dependence of upper critical field and pairing strength on doping in cuprates. Science 2003; 299:86-9. [PMID: 12511645 DOI: 10.1126/science.1078422] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We have determined the upper critical field Hc2 as a function of hole concentration in bismuth-based cuprates by measuring the voltage induced by vortex flow in a driving temperature gradient (the Nernst effect), in magnetic fields up to 45 tesla. We found that Hc2 decreased steeply as doping increased, in both single and bilayer cuprates. This relationship implies that the Cooper pairing potential displays a trend opposite to that of the superfluid density versus doping. The coherence length of the pairs xi(0) closely tracks the gap measured by photoemission. We discuss implications for understanding the doping dependence of the critical temperature Tc0.
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Affiliation(s)
- Yayu Wang
- Department of Physics, Princeton University, Princeton, NJ 08544, USA
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28
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Wang Y, Ong NP, Xu ZA, Kakeshita T, Uchida S, Bonn DA, Liang R, Hardy WN. High field phase diagram of cuprates derived from the Nernst effect. PHYSICAL REVIEW LETTERS 2002; 88:257003. [PMID: 12097120 DOI: 10.1103/physrevlett.88.257003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2002] [Indexed: 05/23/2023]
Abstract
Measurements of the Nernst signal in the vortex-liquid state of the cuprates to high fields (33 T) reveal that vorticity extends to very high fields even close to the zero-field critical temperature T(c0). In overdoped La2-xSrxCuO4, we show that the upper critical field H(c2)(T) curve does not end at T(c0), but at a much higher temperature. These results imply that T(c0) corresponds to a loss in phase rigidity rather than a vanishing of the pairing amplitude. An intermediate field H*(T)<<H(c2)(T) is shown to be the field scale for the flux-flow resistivity.
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Affiliation(s)
- Yayu Wang
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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29
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Tanaka K, Robel I, Jankó B. Electronic structure of multiquantum giant vortex states in mesoscopic superconducting disks. Proc Natl Acad Sci U S A 2002; 99:5233-6. [PMID: 16578872 PMCID: PMC122752 DOI: 10.1073/pnas.082096799] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report self-consistent calculations of the microscopic electronic structure of the so-called giant vortex states. These multiquantum vortex states, detected by recent magnetization measurements on submicron disks, are qualitatively different from the Abrikosov vortices in the bulk. We find that, in addition to multiple branches of bound states in the core region, the local tunneling density of states exhibits Tomasch oscillations caused by the single-particle interference arising from quantum confinement. These features should be directly observable by scanning tunneling spectroscopy.
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Affiliation(s)
- Kaori Tanaka
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439; Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E2; and Department of Physics, University of Notre Dame, Notre Dame, IN 46556-5670
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30
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Zheng GQ, Ozaki H, Kitaoka Y, Kuhns P, Reyes AP, Moulton WG. Delocalized quasiparticles in the vortex state of an overdoped high-T(c) superconductor probed by 63Cu NMR. PHYSICAL REVIEW LETTERS 2002; 88:077003. [PMID: 11863931 DOI: 10.1103/physrevlett.88.077003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2001] [Indexed: 05/23/2023]
Abstract
We report the spin Knight shift (K(s)) and the nuclear spin-lattice relaxation rate (1/T1) in the vortex state as a function of magnetic field (H) up to 28 T in the high-Tc superconductor TlSr2CaCu2O6.8 (Tc = 68 K). At low temperatures well below Tc, both K(s) and 1/T1 measured around the middle point between the two nearest vortices (saddle point) increase substantially with increasing field, which indicate that the quasiparticle states with an ungapped spectrum are extended outside the vortex cores in a d-wave superconductor. The density of states (DOS) around the saddle point is found to be kappaN(0)square root[H/H(c2)], with kappa = 0.5-0.7 and N0 being the normal-state DOS.
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Affiliation(s)
- G-q Zheng
- Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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31
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Capan C, Behnia K, Hinderer J, Jansen AGM, Lang W, Marcenat C, Marin C, Flouquet J. Entropy of vortex cores near the superconductor-insulator transition in an underdoped cuprate. PHYSICAL REVIEW LETTERS 2002; 88:056601. [PMID: 11863761 DOI: 10.1103/physrevlett.88.056601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2001] [Indexed: 05/23/2023]
Abstract
We present a study of Nernst effect in underdoped La(2-x)Sr(x)CuO4 in magnetic fields as high as 28 T. At high fields, a sizable Nernst signal was found to persist in the presence of a field-induced nonmetallic resistivity. By simultaneously measuring resistivity and the Nernst coefficient, we extract the entropy of vortex cores in the vicinity of this field-induced superconductor-insulator transition. Moreover, the temperature dependence of the thermoelectric Hall angle provides strong constraints on the possible origins of the finite Nernst signal above T(c), as recently discovered by Xu et al. [Nature (London) 406, 486 (2000)].
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Affiliation(s)
- C Capan
- Laboratoire de Physique Quantique (UPR5-CNRS), ESPCI, 10 Rue Vauquelin, F-75005 Paris, France
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32
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Hoffman JE, Hudson EW, Lang KM, Madhavan V, Eisaki H, Uchida S, Davis JC. A four unit cell periodic pattern of quasi-particle states surrounding vortex cores in Bi2Sr2CaCu2O8+delta. Science 2002; 295:466-9. [PMID: 11799234 DOI: 10.1126/science.1066974] [Citation(s) in RCA: 733] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Scanning tunneling microscopy is used to image the additional quasi-particle states generated by quantized vortices in the high critical temperature superconductor Bi2Sr2CaCu2O8+delta. They exhibit a copper-oxygen bond-oriented "checkerboard" pattern, with four unit cell (4a0) periodicity and a approximately 30 angstrom decay length. These electronic modulations may be related to the magnetic field-induced, 8a0 periodic, spin density modulations with decay length of approximately 70 angstroms recently discovered in La1.84Sr0.16CuO4. The proposed explanation is a spin density wave localized surrounding each vortex core. General theoretical principles predict that, in the cuprates, a localized spin modulation of wavelength lambda should be associated with a corresponding electronic modulation of wavelength lambda/2, in good agreement with our observations.
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Affiliation(s)
- J E Hoffman
- Department of Physics, University of California, Berkeley, CA 94720-7300, USA
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33
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Berthod C, Giovannini B. Density of states in high- T(c) superconductor vortices. PHYSICAL REVIEW LETTERS 2001; 87:277002. [PMID: 11800909 DOI: 10.1103/physrevlett.87.277002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2001] [Indexed: 05/23/2023]
Abstract
We calculated the electronic structure of a vortex in a pseudogapped superconductor within a model featuring strong correlations. With increasing strength of the correlations, the BCS core states are suppressed and the spectra inside and outside the core become similar. If the correlations are short range, we find new core states in agreement with the observations in YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+delta. Our results point to a common phenomenology for these two systems and indicate that normal-state correlations survive below T(c) without taking part in the overall phase coherence.
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Affiliation(s)
- C Berthod
- DPMC, Université de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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34
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Hoogenboom BW, Kadowaki K, Revaz B, Li M, Renner C, Fischer Ø. Linear and field-independent relation between vortex core state energy and gap in Bi(2)Sr(2)CaCu(2)O(8+delta). PHYSICAL REVIEW LETTERS 2001; 87:267001. [PMID: 11800851 DOI: 10.1103/physrevlett.87.267001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2001] [Indexed: 05/23/2023]
Abstract
We present a scanning tunneling spectroscopy study on quasiparticle states in vortex cores in Bi(2)Sr(2)CaCu(2)O(8+delta). The energy of the observed vortex core states shows an approximately linear scaling with the superconducting gap in the region just outside the core. This clearly distinguishes them from conventional localized core states and is a signature of the mechanism responsible for their discrete appearance in high-temperature superconductors. The energy scaling of the vortex core states also suggests a common nature of vortex cores in Bi(2)Sr(2)CaCu(2)O(8+delta) and YBa(2)Cu(3)O(7-delta). Finally, these states do not show any dependence on the applied magnetic field between 1 and 6 T.
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Affiliation(s)
- B W Hoogenboom
- DPMC, Université de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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35
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Wang QH, Han JH, Lee DH. Staggered currents in the mixed state. PHYSICAL REVIEW LETTERS 2001; 87:167004. [PMID: 11690228 DOI: 10.1103/physrevlett.87.167004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2001] [Indexed: 05/23/2023]
Abstract
The current pattern in the mixed state of high-T(c) superconductors is studied in the U(1) mean-field theory of the t-J model. Assuming the absence of spin antiferromagnetism we find (1) at moderate doping staggered-current pattern exists in vortex cores and eventually percolates with increasing magnetic field. (2) The polarity of the staggered current is pinned by the magnetic field. (3) Vortex cores with (without) staggered current are slightly negatively (positively) charged. (4) Gutzwiller projection does not wash out the staggered current. We discuss the signature of staggered current in neutron scattering and scanning tunneling microscopy.
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Affiliation(s)
- Q H Wang
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
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36
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Mitrović VF, Sigmund EE, Eschrig M, Bachman HN, Halperin WP, Reyes AP, Kuhns P, Moulton WG. Spatially resolved electronic structure inside and outside the vortex cores of a high-temperature superconductor. Nature 2001; 413:501-4. [PMID: 11586354 DOI: 10.1038/35097039] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Puzzling aspects of high-transition-temperature (high-Tc) superconductors include the prevalence of magnetism in the normal state and the persistence of superconductivity in high magnetic fields. Superconductivity and magnetism generally are thought to be incompatible, based on what is known about conventional superconductors. Recent results, however, indicate that antiferromagnetism can appear in the superconducting state of a high-Tc superconductor in the presence of an applied magnetic field. Magnetic fields penetrate a superconductor in the form of quantized flux lines, each of which represents a vortex of supercurrents. Superconductivity is suppressed in the core of the vortex and it has been suggested that antiferromagnetism might develop there. Here we report the results of a high-field nuclear-magnetic-resonance (NMR) imaging experiment in which we spatially resolve the electronic structure of near-optimally doped YBa2Cu3O7-delta inside and outside vortex cores. Outside the cores, we find strong antiferromagnetic fluctuations, whereas inside we detect electronic states that are rather different from those found in conventional superconductors.
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Affiliation(s)
- V F Mitrović
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
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37
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Zhu JX, Ting CS. Quasiparticle states at a d-wave vortex core in high- T(c) superconductors: induction of local spin density wave order. PHYSICAL REVIEW LETTERS 2001; 87:147002. [PMID: 11580671 DOI: 10.1103/physrevlett.87.147002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2001] [Indexed: 05/23/2023]
Abstract
The local density of states (LDOS) at the vortex lattice cores in a high- T(c) superconductor is studied by using a self-consistent mean-field theory including interactions for both antiferromagnetism (AF) and d-wave superconductivity (DSC). In a zero-field optimally doped sample the AF order is completely suppressed while DSC prevails. In the mixed state, we show that the local AF-like spin density wave order appears near the vortex core and acts as an effective local magnetic field on electrons via Zeeman coupling. As a result, the LDOS at the core exhibits a double-peak structure near the Fermi level that is in good agreement with recent scanning tunneling microscopy observations.
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Affiliation(s)
- J X Zhu
- Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA
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38
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Pan SH, O'Neal JP, Badzey RL, Chamon C, Ding H, Engelbrecht JR, Wang Z, Eisaki H, Uchida S, Gupta AK, Ng KW, Hudson EW, Lang KM, Davis JC. Microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x. Nature 2001; 413:282-5. [PMID: 11565024 DOI: 10.1038/35095012] [Citation(s) in RCA: 723] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The parent compounds of the copper oxide high-transition-temperature (high-Tc) superconductors are unusual insulators (so-called Mott insulators). Superconductivity arises when they are 'doped' away from stoichiometry. For the compound Bi2Sr2CaCu2O8+x, doping is achieved by adding extra oxygen atoms, which introduce positive charge carriers ('holes') into the CuO2 planes where the superconductivity is believed to originate. Aside from providing the charge carriers, the role of the oxygen dopants is not well understood, nor is it clear how the charge carriers are distributed on the planes. Many models of high-Tc superconductivity accordingly assume that the introduced carriers are distributed uniformly, leading to an electronically homogeneous system as in ordinary metals. Here we report the presence of an electronic inhomogeneity in Bi2Sr2CaCu2O8+x, on the basis of observations using scanning tunnelling microscopy and spectroscopy. The inhomogeneity is manifested as spatial variations in both the local density of states spectrum and the superconducting energy gap. These variations are correlated spatially and vary on the surprisingly short length scale of approximately 14 A. Our analysis suggests that this inhomogeneity is a consequence of proximity to a Mott insulator resulting in poor screening of the charge potentials associated with the oxygen ions left in the BiO plane after doping, and is indicative of the local nature of the superconducting state.
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Affiliation(s)
- S H Pan
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA.
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39
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Naaman O, Teizer W, Dynes RC. Fluctuation dominated Josephson tunneling with a scanning tunneling microscope. PHYSICAL REVIEW LETTERS 2001; 87:097004. [PMID: 11531592 DOI: 10.1103/physrevlett.87.097004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2001] [Indexed: 05/23/2023]
Abstract
We demonstrate Josephson tunneling in vacuum tunnel junctions formed between a superconducting scanning tunneling microscope tip and a Pb film, for junction resistances in the range 50-300 k Omega. We show that the superconducting phase dynamics is dominated by thermal fluctuations, and that the Josephson current appears as a peak centered at small finite voltage. In the presence of microwave fields ( f = 15.0 GHz) the peak decreases in magnitude and shifts to higher voltages with increasing rf power, in agreement with theory.
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Affiliation(s)
- O Naaman
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0319, USA
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Kishine J, Lee PA, Wen XG. Staggered local density of states around the vortex in underdoped cuprates. PHYSICAL REVIEW LETTERS 2001; 86:5365-5368. [PMID: 11384499 DOI: 10.1103/physrevlett.86.5365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2001] [Indexed: 05/23/2023]
Abstract
We have studied a single vortex with the staggered flux (SF) core based on the SU(2) slave-boson theory of high T(c) superconductors. We find that, whereas the center in the vortex core is a SF state, as one moves away from the core center a correlated staggered modulation of the hopping amplitude chi and pairing amplitude Delta becomes predominant. We predict that in this region the local density of states exhibits staggered modulation when measured on the bonds, which may be directly detected by STM experiments.
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Affiliation(s)
- J Kishine
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Mel'nikov AS. Aharonov-Bohm effect for quasiparticles around a vortex line in a d-wave superconductor. PHYSICAL REVIEW LETTERS 2001; 86:4108-4111. [PMID: 11328107 DOI: 10.1103/physrevlett.86.4108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2000] [Indexed: 05/23/2023]
Abstract
On the basis of the Bogoliubov-de Gennes theory we develop an analytical description of low-energy extended quasiparticle states around an isolated flux line in a superconductor with gap nodes. The wave functions of these excitations and the corresponding density of states are shown to be strongly influenced by the interaction with a pure gauge potential due to the Aharonov-Bohm scenario.
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Affiliation(s)
- A S Mel'nikov
- Institute for Physics of Microstructures, Russian Academy of Sciences 603600, Nizhny Novgorod, GSP-105, Russia
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