Superconductivity in Multiple Interface Geometry: Applicability of Quasiclassical Theory

The method of two-point quasiclassical Green's function is reviewed and its applicability for description of multiple reflections/transmissions in layered structures is discussed. The Green's function of a sandwich built of superconducting layers with a semi-transparent interface is found with the help of recently suggested quasiclassical method [A. Shelankov, and M. Ozana, Phys. Rev. B 61, 7077 (2000)], as well as exactly, from the Gor'kov equation. By the comparison of the results of the two approaches, the validity of the quasiclassical method for the description of real (non-integrable) systems is confirmed.