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Author: Dolgov, O.V. × DDC: 530 ×

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    Bosonic spectral function and the electron-phonon interaction in HTSC cuprates
    (New York : Hindawi Publishing Corporation, 2010) Maksimov, E.G.; Kulić, M.L.; Dolgov, O.V.
    In this paper we discuss experimental evidence related to the structure and origin of the bosonic spectral function α2 F(ω) in high-temperature superconducting (HTSC) cuprates at and near optimal doping. Global properties of α2 F(ω), such as number and positions of peaks, are extracted by combining optics, neutron scattering, ARPES and tunnelling measurements. These methods give evidence for strong electron-phonon interaction (EPI) with 1<λep3.5 in cuprates near optimal doping. We clarify how these results are in favor of the modified Migdal-Eliashberg (ME) theory for HTSC cuprates near optimal doping. In Section 2 we discuss theoretical ingredientssuch as strong EPI, strong correlationswhich are necessary to explain the mechanism of d-wave pairing in optimally doped cuprates. These comprise the ME theory for EPI in strongly correlated systems which give rise to the forward scattering peak. The latter is supported by the long-range part of EPI due to the weakly screened Madelung interaction in the ionic-metallic structure of layered HTSC cuprates. In this approach EPI is responsible for the strength of pairing while the residual Coulomb interaction and spin fluctuations trigger the d-wave pairing. Copyright © 2010 E. G. Maksimov et al.
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    Manifestations of impurity-induced s±⇒s++ transition: Multiband model for dynamical response functions
    (Bristol : IOP, 2013) Efremov, D.; Golubov, A.A.; Dolgov, O.V.
    We investigate the effects of disorder on the density of states, the single-particle response function and optical conductivity in multiband superconductors with s± symmetry of the order parameter, where s± → s++ transition may take place. In the vicinity of the transition, the superconductive gapless regime is realized. It manifests itself in anomalies in the above-mentioned properties. As a result, intrinsically phase-insensitive experimental methods such as angle-resolved photoemission spectroscopy, tunneling and terahertz spectroscopy may be used to reveal information about the underlying order parameter symmetry.