MICROWAVE RESPONSE OF YBA2CU3O6.95 CRYSTALS - EVIDENCE FOR A MULTICOMPONENT ORDER-PARAMETER

New features are reported in precision measurements of the complex mic rowave conductivity of high-quality YBa2Cu3O6.95 crystals grown in BaZ rO3 crucibles. A third peak in the normal conductivity, sigma(1)(T), a t around 80 K, and enhanced pair conductivity sigma(2)(T) below simila r to 65 K are observed. The data are inconsistent with a single order parameter, and instead are indicative of multicomponent superconductiv ity. Overall, these results point to the presence of multiple pairing interactions in YBa2Cu3O6.95 and also provide a natural explanation to account for the low-temperature 35-K conductivity peak observed in al l YBa2Cu3O6.95 crystals.