Effects of anomalous Andreev reflection in high Tc layered structures

Andreev reflection is investigated in layered anisotropic normal metal/superconductor (N/S) systems in the case of an energy gap in S not negligible respect to the Fermi energy, as probably occurring in high critical temperature superconductors (HTS). We find that in these limits retro-reflectivity, which is a fundamental feature of Andreev reflection, is broken modifying sensitively transport across S/N interfaces. This study is extended to aspects proper of HTS junctions to investigate both the supercurrents in S-N-S Josephson structures and zero bound states in S-N contacts respectively. Such an investigation provides a new insight into the effects that anisotropy determines into the phenomenology of HTS grain boundary junctions