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Ishii K, Fujita M, Sasaki T, Minola M, Dellea G, Mazzoli C, Kummer K, Ghiringhelli G, Braicovich L, Tohyama T, Tsutsumi K, Sato K, Kajimoto R, Ikeuchi K, Yamada K, Yoshida M, Kurooka M, Mizuki J. High-energy spin and charge excitations in electron-doped copper oxide superconductors. Nat Commun 2014; 5:3714. [PMID: 24762677 DOI: 10.1038/ncomms4714] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 03/24/2014] [Indexed: 11/09/2022] Open
Abstract
The evolution of electronic (spin and charge) excitations upon carrier doping is an extremely important issue in superconducting layered cuprates and the knowledge of its asymmetry between electron- and hole-dopings is still fragmentary. Here we combine X-ray and neutron inelastic scattering measurements to track the doping dependence of both spin and charge excitations in electron-doped materials. Copper L3 resonant inelastic X-ray scattering spectra show that magnetic excitations shift to higher energy upon doping. Their dispersion becomes steeper near the magnetic zone centre and they deeply mix with charge excitations, indicating that electrons acquire a highly itinerant character in the doped metallic state. Moreover, above the magnetic excitations, an additional dispersing feature is observed near the Γ-point, and we ascribe it to particle-hole charge excitations. These properties are in stark contrast with the more localized spin excitations (paramagnons) recently observed in hole-doped compounds even at high doping levels.
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Affiliation(s)
- K Ishii
- SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan
| | - M Fujita
- Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan
| | - T Sasaki
- Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan
| | - M Minola
- CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - G Dellea
- CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - C Mazzoli
- CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - K Kummer
- European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Grenoble F-38043, France
| | - G Ghiringhelli
- CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - L Braicovich
- CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy
| | - T Tohyama
- 1] Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan [2]
| | - K Tsutsumi
- Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan
| | - K Sato
- Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan
| | - R Kajimoto
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - K Ikeuchi
- Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan
| | - K Yamada
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
| | - M Yoshida
- 1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - M Kurooka
- School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - J Mizuki
- 1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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Ishii K, Tsutsui K, Endoh Y, Tohyama T, Maekawa S, Hoesch M, Kuzushita K, Tsubota M, Inami T, Mizuki J, Murakami Y, Yamada K. Momentum dependence of charge excitations in the electron-doped superconductor Nd1.85 Ce0.15 CuO4: a resonant inelastic x-ray scattering study. PHYSICAL REVIEW LETTERS 2005; 94:207003. [PMID: 16090275 DOI: 10.1103/physrevlett.94.207003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2004] [Indexed: 05/03/2023]
Abstract
We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T(c) superconductor Nd1.85 Ce0.15 CuO4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.
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Affiliation(s)
- K Ishii
- Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, Hyogo 679-5148, Japan.
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Rösch O, Gunnarsson O. Apparent electron-phonon interaction in strongly correlated systems. PHYSICAL REVIEW LETTERS 2004; 93:237001. [PMID: 15601188 DOI: 10.1103/physrevlett.93.237001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Indexed: 05/24/2023]
Abstract
We study the interaction of electrons with phonons in strongly correlated solids, having high-T(c) cuprates in mind. Using sum rules, we show that the apparent strength of this interaction strongly depends on the property studied. If the solid has a small fraction (doping) delta of charge carriers, the influence of the interaction on the phonon self-energy is reduced by a factor delta, while there is no corresponding reduction of the coupling seen in the electron self-energy. This supports the interpretation of recent photoemission experiments, assuming a strong coupling to phonons.
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Affiliation(s)
- O Rösch
- Max-Planck-Institut für Festkörperforschung, D-70506 Stuttgart, Germany
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Rösch O, Gunnarsson O. Electron-phonon interaction in the t-J model. PHYSICAL REVIEW LETTERS 2004; 92:146403. [PMID: 15089562 DOI: 10.1103/physrevlett.92.146403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2003] [Indexed: 05/24/2023]
Abstract
We derive a t-J model with electron-phonon coupling from the three-band model, considering modulation of both hopping and Coulomb integrals by phonons. While the modulation of the hopping integrals dominates, the modulation of the Coulomb integrals cannot be neglected. The model explains the experimentally observed anomalous softening of the half-breathing mode upon doping and a weaker softening of the breathing mode. It is shown that other phonons are not strongly influenced, and, in particular, the coupling to a buckling mode is not strong in this model.
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Affiliation(s)
- O Rösch
- Max-Planck-Institut für Festkörperforschung, D-70506 Stuttgart, Germany
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