We have investigated the transmission of electrons and holes through
interfaces between superconducting aluminum (Tc = 1.2 K) and various normal
non-magnetic metals (copper, gold, palladium, platinum, and silver) using
Andreev-reflection spectroscopy at T = 0.1 K. We analyzed the point contacts
with the modified BTK theory that includes Dynes' lifetime as a fitting
parameter G in addition to superconducting energy gap 2D and normal reflection
described by Z. For contact areas from 1 nm^2 to 10000 nm^2 the BTK Z parameter
was 0.5, corresponding to transmission coefficients of about 80 %, independent
of the normal metal. The very small variation of Z indicates that the
interfaces have a negligible dielectric tunneling barrier. Fermi surface
mismatch does not account for the observed transmission coefficient.Comment: 9 pages, 4 figures, submitted to Proceedings of the 19th
International Conference on Magnetism ICM2012 (Busan 2012