Observation of Unusual Electron Dynamics in High Temperature Superconductors
26 October 1989
Optical spectroscopy of crystals of Ba sub 2 YCu sub 3 O sub (6+x) and La sub (2-X) Sr sub x CuO sub 4 reveal a substantial absorption band in addition to what is expected from the dc transport. This band is unexplained, but its variation with carrier concentration and temperature is suggestive of dipole-active pre-formed pairs. It may be related to the superconductivity since its weight and peak energy shift with T sub c and since its low-energy edge has a strong T-dependence near T sub c.