Superconducting electronic specific heat dependence on temperature: Intrinsic origin of the upturn at low T

The functional dependence of superconducting electronic specific heat on temperature has been derived using the critical field expression obtained by solving the Ginzburg-Landau equation in the elliptic function formalism. At low temperatures the superconducting specific, heat shows an intrinsic upturn. A possible explanation is given. We emphasize the fact that the upturn observed in the specific heat measurements has three main contributions: due to Schottky anomalies under 2 K, due to nuclear coupling under 1 K and an intrinsic contribution to the superconducting state at various temperatures, depending on the magnitude of the linear term of the normal electronic specific heat.