Correlation between the Josephson coupling energy and the condensation energy in bilayer cuprate superconductors

Dominik Munzar, Christian Bernhard, Todd Holden, Andrzej Golnik, Josef Humlíček, and Manuel Cardona
Phys. Rev. B 64, 024523 – Published 21 June 2001
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Abstract

We review some previous studies concerning the intrabilayer Josephson plasmons and present ellipsometric data of the c-axis infrared response of almost optimally doped Bi2Sr2CaCu2O8. The c-axis conductivity of this compound exhibits the same kind of anomalies as that of underdoped YBa2Cu3O7δ. We analyze these anomalies in detail and show that they can be explained within a model involving the intrabilayer Josephson effect and variations of the electric field inside the unit cell. The Josephson coupling energies of different bilayer compounds obtained from the optical data are compared with the condensation energies and it is shown that there is a reasonable agreement between the values of the two quantities. We argue that the Josephson coupling energy, as determined by the frequency of the intrabilayer Josephson plasmon, represents a reasonable estimate of the change of the effective c-axis kinetic energy upon entering the superconducting state. It is further explained that this is not the case for the estimate based on the use of the simplest “tight-binding” sum rule. We discuss possible interpretations of the remarkable agreement between the Josephson coupling energies and the condensation energies. The most plausible interpretation is that the interlayer tunneling of the Cooper pairs provides the dominant contribution to the condensation energy of the bilayer compounds; in other words that the condensation energy of these compounds can be accounted for by the interlayer tunneling theory. We suggest an extension of this theory, which may also explain the high values of Tc in the single-layer compounds Tl2Ba2CuO6 and HgBa2CuO4, and we make several experimentally verifiable predictions.

  • Received 6 March 2001

DOI:https://doi.org/10.1103/PhysRevB.64.024523

©2001 American Physical Society

Authors & Affiliations

Dominik Munzar1,2, Christian Bernhard2, Todd Holden2, Andrzej Golnik2,*, Josef Humlíček1, and Manuel Cardona2

  • 1Department of Solid State Physics, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic
  • 2Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany

  • *Permanent address: IFD, Warsaw University, Hoza, 69, PL-00-681 Warsaw, Poland.

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Vol. 64, Iss. 2 — 1 July 2001

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