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The gap maximum of anisotropic superconductors

R. Combescot
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Abstract

For a completely general anisotropic order parameter (including changes of sign), we show that weak coupling theory is incompatible with high values of the maximum Δ_{M} of the zero temperature gap as compared to the critical temperature T_{c}, such as those found experimentally in Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} where 2 Δ_{M} / T_{c} \approx 7.5 . This gives evidence for strong coupling effects. In particular this comes as a major support for a spin fluctuation mechanism with strong coupling, if one assumes that only a repulsive pairing interaction is at work in high T_{c} superconductors.

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R. Combescot. 1997-10-13. The gap maximum of anisotropic superconductors. https://doi.org/10.1209/epl%2Fi1998-00420-8

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