Nonadiabatiic superconductivity in MgB2 and cuprates

Abstract

The Fermi energy, Ef of newly discovered high-Tc superconductor MgB2 and cuprates is estimated from the measured London penetration depth using a parameter-free expression. Ef of MgB2 and more than 30 lanthanum, yttrium and mercury-based cuprates appears to be about or below 100 meV, depending on doping. There is every evidence that the remarkable low value of Ef and the strong coupling of carriers with high-frequency phonons is the cause of high Tc in all newly discovered superconductors. Taking into account that the carriers mainly reside on oxygen in cuprates, on boron in magnesium diborade, and on carbon in doped fullerenes, these superconductors form what is essentially $nonadiabatic$ 'metallic' oxygen, boron and carbon, respectively. The boron isotope effect on the carrier mass in magnesium-diboride similar to the oxygen isotope effect on the supercarrier mass observed by Guo-meng Zhao et al. in cuprates is predicted.

4 pages, 1 table, submitted to Physical Review

References in corpus (3)

• Boron Isotope Effect in Superconducting MgB${}_2$
• Phase Fluctuations and Pseudogap Phenomena
• Evidence for novel polaronic Fermi-liquid in doped oxides

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• Lorenz number in high Tc superconductors: evidence for bipolarons
• Hall effect and resistivity in underdoped cuprates
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• Absence of a boron isotope effect in the magnetic penetration depth of MgB${}_2$
• Isotope effects in high-Tc cuprate superconductors: Ultimate proof for bipolaron theory of superconductivity
• Theory of quantum magneto-oscillations in underdoped cuprate superconductors
• Diamagnetism of real-space pairs above Tc in hole doped cuprates
• Breakdown of the Wiedemann-Franz law in strongly-coupled electron-phonon system, application to the cuprates
• High temperature superconductivity due to the long-range electron-phonon interaction, application to isotope effects, thermomagnetic transport and nanoscale heterogeneity in cuprates
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• Effect of interband interactions of phonon and charge fluctuation on superconducting parameters of MgB2
• Unconventional phonon-mediated superconductivity in MgB_{2}
• Superlight bipolarons and criterion of BCS-BEC crossover in cuprates
• Hall-Lorenz ratio of YBa2Cu3O7 using Ionization energy based Fermi-Dirac statistics and charge-spin separation
• A minimal size for granular superconductors
• Bipolaronic proximity and other unconventional effects in cuprate superconductors