A-B PLANE MICROWAVE SURFACE IMPEDANCE OF A HIGH-QUALITY BI2SR2CACU2O8SINGLE-CRYSTAL

The a-b plane microwave surface impedance of a high-quality Bi2Sr2CaCu 2O8 single crystal (T-c approximate to 93 K) has been measured at 14.4 , 24.6, and 34.7 GHz. The surface resistance at low temperature is the lowest yet reported, is comparable with the best YBa2Cu3O7-delta data , and has a characteristic omega(2) frequency dependence. The change i n penetration depth, Delta lambda(ab)(T), has a strong linear term at low temperature which is consistent with a gap with line nodes on the Fermi surface. The real part of the microwave conductivity displays a broad peak at low temperature, similar to that observed in YBa2Cu3O7-d elta.