Infrared Properties of Selected High Tc Superconductors

We wish to investigate to what extent the infrared properties of cuprates are similar to and different from that of ordinary metals and superconductors. We therefore examine and discuss the infrared reflectivity and conductivity in the normal and superconducting states for various optimally doped and under-doped cuprates. We focus on the conductivity of the uplanes in compounds with high Tc, bulk superconductivity. There we find a very simple but unusual normal state phenomenology, as well as evidence for a transition to superconductivity that is very different from the conventional gap opening transition of BCS theory.