Superconductivity in quasi-two-dimensional nonadiabatic systems with arbitrary charge-carrier density at T=0

摘要

The basic system of equations of the theory of superconductivity at T=0 is obtained in an approximation linear in the nonadiabaticity, and analytic solutions for the order parameter Δ and the chemical potential μ are found in two limiting cases: μΔ, and μ～Δ. The dependence of these quantities on the density of charge carriers is investigated. It is found that the order parameter Δ can be increased by a factor of four to five in comparison with ordinary superconductors owing to the effects of nonadiabaticity and strong electronic correlations. The influence of the nonadiabaticity on the BCS-Bose crossover in the region of low chargecarrier densities is also investigated.