On the Bilayer Coupling in the Yttrium-Barium Family of High Temperature Superconductors

A. J. Millis; H. Monien

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On the Bilayer Coupling in the Yttrium-Barium Family of High Temperature Superconductors

A. J. Millis·H. Monien

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Abstract

We present and solve a model for the susceptibility of two CuO2 planes coupled by an interplane coupling J_perp and use the results to analyze a recent "cross-relaxation" NMR experiment on Y2Ba4Cu7O15. We deduce that in this material the product of J_perp and the maximum value of the in-plane susceptibility chi_max varies from approximately 0.2 at T = 200 K to 0.4 at T = 120 K and that this implies the existence of a temperature dependent in-plane spin correlation length. Using estimates of chi_max from the literature we find 5 meV < J_perp < 20 meV. We discuss the relation of the NMR results to neutron scattering results which have been claimed to imply that in YBa2Cu3O_{6+x} the two planes of a bilayer are perfectly anticorrelated. We also propose that the recently observed 41 meV excitation in YBa2Cu3O7 is an exciton pulled down below the superconducting gap by J_perp.

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A. J. Millis, H. Monien. 1995-06-20. On the Bilayer Coupling in the Yttrium-Barium Family of High Temperature Superconductors. https://arxiv.org/abs/cond-mat/9506088

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