R. Szczesniak, A. P. Durajski, D. Szczesniak
The structure of the gap parameter ($\Delta_{\kvec}$) for the hole-doped cuprates has been studied in the paper. In the first step, the equation for the anisotropic anomalous thermal average ($\phi_{\kvec}$) has been solved close to the Fermi energy. The obtained results indicate the $\phi_{\kvec}$-amplitude crossover from the d-wave BCS to non-BCS behavior, as the electron-electron-phonon potential increases. In consequence, the antinodal part of the gap parameter is very weak temperature dependent and above the critical temperature ($T_{C}$), it extends into the anomalous normal state to the pseudogap temperature. On the other hand, the values of $\Delta_{\kvec}$, which are close to the nodal part, are temperature dependent and they disappear for $T>T_{C}$. The presented results strongly suggested that the pseudogap in the hole-doped cuprates is connected with the antinodal part of $\Delta_{\kvec}$. The model has been tested for the ${\rm YBa_{2}Cu_{3}O_{7-\delta}}$ superconductor. It has been shown that the theoretical results agree with the experimental data.
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http://arxiv.org/abs/1302.2450
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