Healing length of the superconducting order parameter

Using the Bardeen-Kilmmel-Jacobs-Tewordt approach to the BCS theory of a nonuniform superconductor, we study the problem of a semi-infinite superconductor with a rigid potential barrier at the interface. Very close to T-c, the spatial variation of the order parameter is given by the Ginzburg-Landau formula Delta (z, T)/Delta(infinity)(T) = tanh[z/root 2 xi(GL)(T)]. At decreasing temperatures, however, the order parameter heals much more rapidly than xi(T) = v(F)/pi Delta(infinity)(T), where xi(LM)(T) = lim 0.74 xi(T) as T -> T-.c; and, at low and intermediate temperatures, does so over atomic distances.