Theory of High Temperature Superconductivity Beyond BCS with Realistic Coulomb and Fröhlich Interactions

Alexandrov, A. S.

doi:10.1007/s10948-012-2098-8

Cited by 3 publications

(2 citation statements)

References 27 publications

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“…It not only describes the specific physical properties of charge carriers in polarizable solid, but also constitutes an interesting field theoretical model consisting of a fermion interacting with a scalar boson field 2 . Even today, there is ongoing research on polarons, including the basic theory 3 , as well as their behaviour in more compelling situations such as high-temperature superconductors 4 5 6 and colossal magnetoresistance in rare-earth manganites 7 .…”

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Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

et al. 2015

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The polaron is a quasi-particle formed by a conduction electron (or hole) together with its self-induced polarization in a polar semiconductor or an ionic crystal. Among various polarizable examples of complex oxides, strontium titanate (SrTiO3) is one of the most studied. Here we examine the carrier type and the interplay of inner degrees of freedom (for example, charge, lattice, orbital) in SrTiO3. We report the experimental observation of Fröhlich polarons, or large polarons, at the bare SrTiO3 surface prepared by vacuum annealing. Systematic analyses of angle-resolved photoemission spectroscopy and X-ray absorption spectra show that these Fröhlich polarons are two-dimensional and only exist with inversion symmetry breaking by two-dimensional oxygen vacancies. Our discovery provides a rare solvable field theoretical model, and suggests the relevance of large (bi)polarons for superconductivity in perovskite oxides, as well as in high-temperature superconductors.

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Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

et al. 2015

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“…[, p. 4] that “cuprate bipolarons are relatively light because they are inter‐site rather than on‐site pairs due to the strong on‐site repulsion, and because mainly c‐axis polarized optical phonons are responsible for the in‐plane mass renormalization.” See for instance refs. [] and the references therein.…”

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Isotropic Bipolaron–Fermion Exchange Theory and Unconventional Pairing in Cuprate Superconductors

2018

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The appearance of unconventional pairing in superconducting cuprates is examined from a microscopic model, taking into account important properties of hole-doped copper oxides. An exchange interaction between fermions and dominantly inter-site bipolarons is considered to be the mechanism which leads to the pairing. Its momentum dependency is connected to the well-established fermion-phonon anomalies in cuprate superconductors. Since charge carriers in these materials are strongly correlated, a screened Coulomb repulsion is added to this exchange term. Any ad hoc assumptions like anisotropy are avoided, but a microscopic explanation of unconventional pairing for coupling strengths that are in accordance with experimental facts is provided. One important outcome is a mathematically rigorous elucidation of the role of Coulomb repulsion in unconventional pairing, which is shown to be concomitant with a strong depletion of superconducting pairs. The theory, applied to the special case of LaSr 214, predicts at optimal doping i) a coherence length of 21Å, which is the same as that obtained from the Ginzburg-Landau critical magnetic field measured for this material, and ii) d-wave pair formation in the pseudogap regime, that is, at temperatures much higher than the superconducting transition temperature.

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The Development of High-Temperature Superconductors and 2D Iron-Based Superconductors

Geng

2019

Nano-Sized Multifunctional Materials

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Theory of High Temperature Superconductivity Beyond BCS with Realistic Coulomb and Fröhlich Interactions

Cited by 3 publications

References 27 publications

Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface

Isotropic Bipolaron–Fermion Exchange Theory and Unconventional Pairing in Cuprate Superconductors

The Development of High-Temperature Superconductors and 2D Iron-Based Superconductors

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