Abstract
There are two essential attributes of electrons for superconductivity: mobility and pairing. While this is not directly obvious, these two attributes compete against each other. High-temperature superconductivity may be obtained by combining two-components, one which provides pairing and the other mobility. In the local-strong-pairing (negative-U lattice) limit of superconductivity Tc is controlled by the hopping of electron pairs rather than by the pair binding energy. Coupling a negative-U lattice to delocalized electron states increases the hopping and thus the critical temperature. In parallel, Cooper-pair superconductivity is induced in the delocalized electrons. In the normal state both Bosonic and Fermionic states exist, and below Tc Bosonic states exist in the Fermionic gap. It is suggested that superconductivity in the new class of oxide superconductors is due to locally paired electrons on the lattice of oxygen vacancies combined with conducting metal-oxide layers. The discussion includes the superconducting properties Tc, Δ, Hc and ξ, long wave collective excitations, normal state properties including resistance and tunneling, and the isotope shift. Unusual properties are predicted including neutral Fermion excitations due to hybridization of electrons and holes, a spreading of the Femionic gap onset, a separation between the resistive transition Tc’ and the evaporation of the condensate Tc, anomalies in sound and bulk modulii at Tc, linear temperature dependence of normal state resistivity, linear voltage dependence in normal state tunneling conductance, and finite zero bias conductance in superconducting state tunneling. A new signature of structural coherence which can be seen in channeling experiments and other structural probes is indicated.
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References
G. A. Baraff, E. O. Kane, and M. Schlüter, Phys. Rev. B 21, 5662 (1980); G. D. Watkins and J. R. Troxell, Phys. Rev. Lett. 44, 593 (1980); D. Vanderbilt and J. D. Joannopoulos, Phys. Rev. Lett. 49, 823 (1982); R. Car, P. Kelly, A. Oshiyama, S. T. Pantelides, Phys. Rev. Lett. 52, 1814 (1984); Y. Bar-Yam and J. D. Joannopoulos, Phys. Rev. Lett. 56, 2203 (1986)
The direct involvement of oxygen vacancies in superconductivity has been discussed by J. C. Phillips without explicitly considering real space pairing, see Phys. Rev. Lett. 59, 1856 (1987); Phys. Rev. B 39, 7356 (1989) and unpublished.
W. E. Pickett, Rev. Mod. Phys. 61, 433 (1989)
P. Nozieres and S. Schmitt-Rink, J. Low Temp. Phys. 59, 195 (1985); C. M. Varma, Phys. Rev. Lett. 61, 2713 (1988); S. Robaszkiewicz, R. Micnas, and K. A. Chao, Phys. Rev. B 23, 1447 (1981) and 24, 1579 (1981).
P. Nozieres and S. Schmitt-Rink, J. Low Temp. Phys. 59, 195 (1985)
Metastable Bosons in a two-component formulation are discussed as early as M. R. Schafroth, Phys. Rev. 96, 1442 (1954); and more recently by J. Ranninger and S. Robaszkiewicz, Physica 125B, 468 (1985); S. P. Ionov, Izv. Akad. Nauk SSSR Ser. Fiz. 49, 310 (1985); G. M. Éliashberg, JETP Lett. Vol. 46, S81 (1987); D. M. Newns Phys. Rev. B 36, 5595 (1987); D. M. Newns, M. Rasolt, and P. C. Pattnaik, Phys. Rev. B 38, 6513 (1988); J. Ranninger, R. Micnas, and S. Robaszkiewicz, Ann. Phys. Fr. 13, 455 (1988); R. Freidberg and T. D. Lee, Phys. Lett. A 138, 423 (1989); Phys. Rev. B 40, 6745-6762 (1989); L. P. Gorkov and G. M. Éliashberg, JETP Lett. Vol. 46, S84 (1987); R. Micnas, J. Ranninger, S. Robaszkiewicz, Rev. Mod. Phys. 62, 113(1990)
E. Simánek, Solid State Comm. 32, 731 (1979); C. S. Ting, D. N. Talwar, and K. L. Ngai Phys. Rev. Lett. 45, 1213 (1980); H.-B. Schüttler, M. Jarrell and D. J. Scalapino Phys. Rev. Lett. 58, 1147 (1987); Phys. Rev. B 39, 6501 (1989). In this work both components are treated equally.
Other possible terms in the Hamiltonian include a coupled charge density wave promoting term. It does not change the results, near μ=EB/2, because it competes against the large t term, and tne possible CDW small induced gap need not coincide with EB/2.
M. Tinkham, “Introduction to Superconductivity”, Mcgraw-Hill, NY (1975)
Structural relaxation dynamical effects have not been included.
This neglects special density-of-states enhancements, particularly in quasi-two dimensional systems, see J. E. Hirsch and D. J. Scalapino, Phys. Rev. Lett. 56, 2732 (1986)
Even in the special 2-D nearest neighbor case this model does not suffer from the competition between charge-density-wave and superconducting order. The charge density wave order results from the nearest neighbor repulsion. R. T. Scalettar, E. Y. Loh, J. E. Gubernatis, A. Moreo, S. R. White, D. J. Scalapino, R. L. Sugar and E. Dagotto Phys. Rev. Lett. 62, 1407 (1989)
The integral is the same as that used for determining the BCS Tc but its use is significantly different.
Oxygen vacancies in Cu-0 based superconductors lower Dc(μ). Tc can thus be lowered as oxygen vacancies are added in the large concentration limit even though they are essential to superconductivity.
“Theory of quantum liquids” D. Pines and P. Nozières (Benjamin, NY, 1966)
P. A. Lee and N. Read, Phys. Rev. Lett. 58, 2691 (1987)
The breakdown of the quasi-particle picture may happen earlier. In any case Tc occurs in the region of rapidly decreasing Δ’(T) so Tc’(μ) is of order Tc(μ).
“Solid State Physics”, W. A. Harrison, (p. 333)
Z. Vardeny and J. Tauc, Phys. Rev. Lett. 54, 1844 (1985)
Y. Bar-Yam, J. D. Joannopoulos and D. Adler Phys. Rev. Lett. 54, 1844 (1985)
A. J. Heeger, S. Kivelson, J. R. Schrieffer, and W.-P. Su Rev. Mod. Phys. 60, 781 (1988)
Y. Bar-Yam (unpublished)
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Bar-Yam, Y. (1990). Two-Component Superconductivity. In: Avishai, Y. (eds) Recent Progress in Many-Body Theories. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-3798-4_8
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