TUNNELING AND INFRARED-SPECTROSCOPY ON HIGH-T(C) SUPERCONDUCTORS

We have investigated single crystals of Bi2Sr2Ca1-xYxCu2O8 (x=0 - 0.35 ) by far infrared transmission spectroscopy and by break junction tunn eling. The junctions were made at low temperatures in vacuum, and SIS tunneling was measured at various temperatures and magnetic fields. Th e tunneling results are interpreted in terms of a Josephson current an d a single electron tunneling density of states (DOS). Although the DO S is found to be zero at the Fermi level, we do not see a fully develo ped gap even at temperatures well below the critical temperature. Ther e is qualitative agreement between tunneling and infrared spectroscopy results.