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Abstract

High- superconductors are characterized by a short coherence length . From the quasi-2D structure of these compounds, we calculate the density of states , the Fermi velocity and the gap energy . From these parameters, we deduce a formula of the coherence length . We study the effect of the phonon-interaction , the effective mass of carriers and the Coulomb repulsion on the coherence length . We show that when the coupling constant is in the range 0.06 – 0.30 and the effective mass is between 2m0 and 6m0 (m0 is the free electron mass), the values obtained of the coherence length and the gap energy are in a good agreement with experimental results.