Energy gap in local-pair superconductors

A theoretical model1 of high-Tc superconductivity is analyzed. A superconducting transition in a system of local electron pairs interacting through the conduction band is shown to result in the emergence of two energy gaps: the tunneling gap (the gap in the one-electron excitation spectrum) ΔS (k) and the far-infrared gap (“pair gap”) Δp. The former of these gaps is large in comparison with the value predicted by the BCS theory and is sharply anisotropic in the k-space, while the latter exhibits an anomalous temperature dependence (in particular, it remains finite at the transition point Tc). The magnitude of the ratio 2Δp/k Tc ∼ 2. The interband absorption of a high-temperature superconductor has singularities at energies ℏω = 2Δp, 2ΔS and 2Δs ± 2Δp whose amplitude depends on temperature. Some peculiarities vanish at T = 0.

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