Formation of Self-Energy Singularities by Thermal Fluctuations of the Superconducting Order Parameter

We investigate the structure of the energy dependence of the normal and anomalous self-energy components of the one-particle Green function in the superconducting state, which is calculated with account for charge carrier scattering by thermal fluctuations of electron-hole pairs. Analysis is performed using the self-consistent theory of continual integration based on the quasi-two-dimensional single-band model with attraction between electrons at neighboring sites. Asymptotic expressions for the self-energy components, which coincide in structure with analogous expressions of the phenomenological model of hybridization of electrons with hidden fermionic excitations, are obtained in the average t-matrix approximation. Analysis of the results shows that the energy dependences of both self-energy components have characteristic peaks that suppress each other in the total self-energy at low temperatures. Such a behavior is preserved in the range of anomalously low temperatures and disappears only in the quantum limit for T -> 0, in which quantum fluctuations play the decisive role. With increasing temperature, the mutual suppression is replaced by mutual enhancement followed by mutual compensation in the range of temperatures close to the superconducting transition temperature.