c-axis phonons and the enhancement of pairing correlations in high-temperature superconductors |
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Authors: | M. Mierzejewski and J. Zieliski |
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Affiliation: | (1) Institute of Physics, University of Silesia, 40-007 Katowice, Poland |
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Abstract: | We consider the two-dimensional Hubbard model including electron-phonon interaction. Strong local correlations (U limit) are taken into account within the mean-field approximation for auxiliary boson fields. Phonon-assisted transitions between intraand interlayer states are introduced as the source of coupling between two-dimensional CuO2 layers. This type of processes effectively leads to the nonlinear (quadratic) interaction of intralayer electrons withc-axis phonons. We construct the Eliashberg equations for the resulting Hamiltonian and evaluate the superconducting transition temperatureTc. Our model calculation demonstrates that a pronounced enhancement ofTc in thed-wave channel is possible. The largest enhancement ofTc tends to take place for small hole concentrations. This means that the coupling toc-axis phonons could compete with two-dimensional correlations responsible for the onset of antiferromagnetic order. It is remarkable that the two-dimensional features in the normal state are hardly affected by this specific interlayer interaction. Therefore,c-axis two-phonon-mediated interlayer coupling can cooperate with interlayer pair tunneling and substantially contribute to an increased pairing. |
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Keywords: | High-temperature superconductivity two-dimensional Hubbard model Eliashberg equation |
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