Optical Properties of High T sub c Superconductors
17 February 1988
The frequency-dependent conductivity of Cu-O based superconductors is found to vary from sample to sample even in single-phase, bulk (twinned) crystals. Important questions remain unsatisfactorily answered regarding excitations between 0.1 and 1.0eV and at lower energies near the expected superconducting energy gap.