Electron transmission in normal/heavy-fermion superconductor junctions

The Andreev reflection between a normal metal (N) and a heavy-fermion superconductor (HFS) is studied and the boundary conditions for the electron's wave function in the two systems are established in the framework of a two band model for the HFS. Hence we show in a simple and explicit way that the mass enhancement factors in the heavy-fermion (HF) metal do not cause impedance at the N/HFS interface, in accordance with arguments previously presented. We also present an extension of the theory to a two-fluid model for the heavy-fermion, as possibly applicable to, e.g., CeCoIn_5.