DETERMINATION OF THE GAP DISTRIBUTION IN YBA2CU3O7 USING A FAR-INFRARED REFLECTION-FABRY-PEROT DEVICE

This paper reports on far-infrared measurements of YBa2Cu3O7 films oriented with the c-axis perpendicular to the surface, by using a silicon reflection Fabry-Perot interferometer as a multireflection device. From these we could derive the dielectric function, the refractive index, the field penetration depth and the surface impedance of the material. The one order of magnitude higher sensitivity of the method compared to a direct reflectance measurement allowed to find an almost continuous gap distribution in the 70-215 cm-1 region together with a separate gap at about 330 cm-1. A quasizero gap absorption is found down to 20 cm-1 even at low temperatures (10 K).