Barga Jazz Festival 2020 – Extended Singularity

Fulvio Sigurtà – tromba | Stefano Onorati – pianoforte | Gabriele Evangelista – contrabbasso | Alessandro Paternesi – batteria




An equation for determining the superconducting transition temperature Tc is obtained in the linear approximation in the nonadiabaticity for a system with a square-root singularity in the electron density of states. The vertex function is calculated and analytical expressions are obtained for Tc in the limiting cases Tc≪μ1 and μ1=0(μ1 is the singular point) and also an expression for the coefficient of the isotope effect. It is shown that the contribution of nonadiabatic effects to Tc is significant and decreases on approach to the singular point μ1=0, and the smallness of the isotope effect is due to the presence of such a singularity in the electron energy spectrum and the nonadiabaticity of the system