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Rusydi A, Goos A, Binder S, Eich A, Botril K, Abbamonte P, Yu X, Breese MBH, Eisaki H, Fujimaki Y, Uchida S, Guerassimova N, Treusch R, Feldhaus J, Reininger R, Klein MV, Rübhausen M. Electronic screening-enhanced hole pairing in two-leg spin ladders studied by high-resolution resonant inelastic x-ray scattering at Cu M edges. PHYSICAL REVIEW LETTERS 2014; 113:067001. [PMID: 25148343 DOI: 10.1103/physrevlett.113.067001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Indexed: 05/23/2023]
Abstract
We study the electronic screening mechanisms of the effective Coulomb on-site repulsion in hole-doped Sr(14)Cu(24)O(41) compared to undoped La(6)Ca(8)Cu(24)O(41) using polarization dependent high-resolution resonant inelastic x-ray scattering at Cu M edges. By measuring the energy of the effective Coulomb on-site repulsion and the spin excitations, we estimate superexchange and hopping matrix element energies along rungs and legs, respectively. Interestingly, hole doping locally screens the Coulomb on-site repulsion reducing it by as much as 25%. We suggest that the increased ratio of the electronic kinetic to the electronic correlation energy contributes to the local superexchange mediated pairing between holes.
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Affiliation(s)
- A Rusydi
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany and NUSSNI-NanoCore, Department of Physics, National University of Singapore, Singapore 117542, Singapore and Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - A Goos
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany
| | - S Binder
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany
| | - A Eich
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany
| | - K Botril
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany
| | - P Abbamonte
- Physics Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - X Yu
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - M B H Breese
- NUSSNI-NanoCore, Department of Physics, National University of Singapore, Singapore 117542, Singapore and Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - H Eisaki
- Nanoelectronics Research Institute, AIST, 1-1-1 Central 2, Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Y Fujimaki
- Department of Superconductivity, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
| | - S Uchida
- Department of Superconductivity, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan
| | - N Guerassimova
- Photon Science, DESY, Notkestraße 85, D-22607 Hamburg, Germany
| | - R Treusch
- Photon Science, DESY, Notkestraße 85, D-22607 Hamburg, Germany
| | - J Feldhaus
- Photon Science, DESY, Notkestraße 85, D-22607 Hamburg, Germany
| | - R Reininger
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - M V Klein
- Physics Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA
| | - M Rübhausen
- Institut für Angewandte Physik, Universität Hamburg, Jungiusstraße 11, D-20355 Hamburg, Germany and Center for Free Electron Laser Science (CFEL), Notkestraße 85, D-22607 Hamburg, Germany and NUSSNI-NanoCore, Department of Physics, National University of Singapore, Singapore 117542, Singapore
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Comin R, Levy G, Ludbrook B, Zhu ZH, Veenstra CN, Rosen JA, Singh Y, Gegenwart P, Stricker D, Hancock JN, van der Marel D, Elfimov IS, Damascelli A. Na2IrO3 as a novel relativistic Mott insulator with a 340-meV gap. PHYSICAL REVIEW LETTERS 2012; 109:266406. [PMID: 23368593 DOI: 10.1103/physrevlett.109.266406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Indexed: 06/01/2023]
Abstract
We study Na2IrO3 by angle-resolved photoemission spectroscopy, optics, and band structure calculations in the local-density approximation (LDA). The weak dispersion of the Ir 5d-t(2g) manifold highlights the importance of structural distortions and spin-orbit (SO) coupling in driving the system closer to a Mott transition. We detect an insulating gap Δ(gap)≃340 meV which, at variance with a Slater-type description, is already open at 300 K and does not show significant temperature dependence even across T(N)≃15 K. An LDA analysis with the inclusion of SO and Coulomb repulsion U reveals that, while the prodromes of an underlying insulating state are already found in LDA+SO, the correct gap magnitude can only be reproduced by LDA+SO+U, with U=3 eV. This establishes Na2IrO3 as a novel type of Mott-like correlated insulator in which Coulomb and relativistic effects have to be treated on an equal footing.
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Affiliation(s)
- R Comin
- Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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Giovannetti G, Kumar S, Stroppa A, van den Brink J, Picozzi S. Multiferroicity in TTF-CA organic molecular crystals predicted through ab initio calculations. PHYSICAL REVIEW LETTERS 2009; 103:266401. [PMID: 20366325 DOI: 10.1103/physrevlett.103.266401] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Indexed: 05/29/2023]
Abstract
We show by means of ab initio calculations that the organic molecular crystal TTF-CA is multiferroic: it has an instability to develop spontaneously both ferroelectric and magnetic ordering. Ferroelectricity is driven by a Peierls transition of the TTF-CA in its ionic state. Subsequent antiferromagnetic ordering strongly enhances the opposing electronic contribution to the polarization. It is so large that it switches the direction of the total ferroelectric moment. Within an extended Hubbard model, we capture the essence of the electronic interactions in TTF-CA, confirm the presence of a multiferroic groundstate, and clarify how this state develops microscopically.
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Affiliation(s)
- Gianluca Giovannetti
- Consiglio Nazionale delle Ricerche-Istituto Nazionale per la Fisica della Materia (CNR-INFM), CASTI Regional Laboratory, 67100 L'Aquila, Italy
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