Book contents
- Frontmatter
- Contents
- Preface
- 1 A polaron theory of high-temperature superconductors
- 2 On the possibility of non-BCS superconductivity
- 3 A bipolaron Bose liquid in high-Tc superconductors
- 4 Spin polarons in high-Tc superconductors
- 5 The polaron scenario for high-Tc superconductors
- 6 Formation, phase separation and superconductivity of large bipolarons
- 7 Polarons and bipolarons in WO3−x and YBa2Cu3O7
- 8 Polaron bands in the far- and mid-infrared spectra of e-doped cuprates
- 9 Electron–phonon interaction of non-equilibrium carriers in the photoinduced state of YBa2Cu3O7−δ
- 10 Experimental evidence of local lattice distortion in superconducting oxides
- 11 The Hall effect due to small polarons and conduction in narrow energy bands
- 12 Static and dynamic conductivity of untwinned Y1Ba2Cu4O8: gaps or condensation?
- 13 The near infrared and optical absorption of high- Tc superconductors using powders
- 14 Polaronic theory of mid-infrared conductivity: a numerical cluster study
- 15 Electromagnetic properties of local pair superconductors
- 16 Electron–hole asymmetric polarons
- 17 On the nature of the superconducting state in high-Tc cuprates
- 18 High- Tc superconductivity with polarons and bipolarons: an approach from the insulating states
- 19 Coexistence of small-polaron and Anderson localization in high- Tc superconducting materials
- 20 Concentration and temperature-dependence of magnetic polaron spectra in the t–J model
- 21 Mass enhancement without band-narrowing in t–t′–J and related models: predictions for Fermi-surface and optical conductivity
- 22 Polarons in Peierls–Hubbard models
- 23 Exact estimates of inter-polaron coupling constants resulting in bipolaron formation
- 24 Coulomb interaction and the criteria for bipolaron formation
- 25 Large bipolarons and high-Tc materials
- 26 Collective excitations in the ground state of a two-dimensional attractive Fermi gas
- 27 Strong two-band electron self-trapping, state hybridization effects and related pressure-induced phenomena in semiconductors
- 28 Bismuth disproportionation in super- and semiconducting barium bismuthates
- 29 Magnetic polarons in concentrated and diluted magnetic semiconductors
- 30 Energy scales of exotic superconductors
- Index
4 - Spin polarons in high-Tc superconductors
Published online by Cambridge University Press: 24 November 2009
- Frontmatter
- Contents
- Preface
- 1 A polaron theory of high-temperature superconductors
- 2 On the possibility of non-BCS superconductivity
- 3 A bipolaron Bose liquid in high-Tc superconductors
- 4 Spin polarons in high-Tc superconductors
- 5 The polaron scenario for high-Tc superconductors
- 6 Formation, phase separation and superconductivity of large bipolarons
- 7 Polarons and bipolarons in WO3−x and YBa2Cu3O7
- 8 Polaron bands in the far- and mid-infrared spectra of e-doped cuprates
- 9 Electron–phonon interaction of non-equilibrium carriers in the photoinduced state of YBa2Cu3O7−δ
- 10 Experimental evidence of local lattice distortion in superconducting oxides
- 11 The Hall effect due to small polarons and conduction in narrow energy bands
- 12 Static and dynamic conductivity of untwinned Y1Ba2Cu4O8: gaps or condensation?
- 13 The near infrared and optical absorption of high- Tc superconductors using powders
- 14 Polaronic theory of mid-infrared conductivity: a numerical cluster study
- 15 Electromagnetic properties of local pair superconductors
- 16 Electron–hole asymmetric polarons
- 17 On the nature of the superconducting state in high-Tc cuprates
- 18 High- Tc superconductivity with polarons and bipolarons: an approach from the insulating states
- 19 Coexistence of small-polaron and Anderson localization in high- Tc superconducting materials
- 20 Concentration and temperature-dependence of magnetic polaron spectra in the t–J model
- 21 Mass enhancement without band-narrowing in t–t′–J and related models: predictions for Fermi-surface and optical conductivity
- 22 Polarons in Peierls–Hubbard models
- 23 Exact estimates of inter-polaron coupling constants resulting in bipolaron formation
- 24 Coulomb interaction and the criteria for bipolaron formation
- 25 Large bipolarons and high-Tc materials
- 26 Collective excitations in the ground state of a two-dimensional attractive Fermi gas
- 27 Strong two-band electron self-trapping, state hybridization effects and related pressure-induced phenomena in semiconductors
- 28 Bismuth disproportionation in super- and semiconducting barium bismuthates
- 29 Magnetic polarons in concentrated and diluted magnetic semiconductors
- 30 Energy scales of exotic superconductors
- Index
Summary
Abstract
The spin-polaron concept is introduced in analogy to ionic and electronic polarons and the assumptions underlying the author's approach to spinpolaron-mediated high-Tc superconductivity are discussed. Elementary considerations about the spin-polaron formation energy are reviewed and the possible origin of the pairing mechanism illustrated schematically. The electronic structure of the CuO2 planes is treated from the standpoint of antiferromagnetic band calculations that lead directly to the picture of holes predominantly on the oxygen sublattice in a Mott–Hubbard/charge transfer insulator. Assuming the holes to be described in a Bloch representation but with the effective mass renormalized by spin-polaron formation, equations for the superconducting gap, Δ, and transition temperature, Tc, are developed and the symmetry of Δ discussed. After further simplifications, Tc is calculated as a function of the carrier concentration, x. It is shown that the calculated behavior of Tc(x) follows the experimental results closely and leads to a natural explanation of the effects of under- and over-doping. The paper concludes with a few remarks about the evidence for the carriers being fermions (polarons) or bosons (bipolarons).
Introduction
A carrier (electron or hole) moving through an ionic lattice will induce displacements of the ions and, under certain conditions, the carrier plus ionic displacements may form a good quasi-particle, i.e., the ionic polaron [1]. Similarly, electronic polarons may form when the carriers induce polarization of localized or quasi-localized electronic distributions. In an analagous manner, a spin polaron is a spin ½ carrier moving in a magnetic medium accompanied by deviations of localized ionic spins.
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- Publisher: Cambridge University PressPrint publication year: 1995