Nonlocal fluctuation effects in clean superconductor

The theory of fluctuation conductivity for an arbitrary impurity concentration including ultra-clean limit ($T_\tau\gg\sqrt{T_c/T-T_c}$) is developed. It is demonstrated that the formal divergency of the fluctuation density of states contribution obtained previously for the clean case is removed by the correct treatment of the nonlocal ballistic electron scattering. We show that in the ultra-clean limit the density-of-states quantum corrections are canceled by the Maki–Thompson term and only classical paraconductivity remains.