TUNNELING STUDIES IN BISRCACUO-PB BREAK JUNCTIONS

Single-particle tunnelling experiments have been performed on polycrys talline BiSrCaCuO:Pb using break junction configuration in the tempera ture range 42 K less than or equal to T less than or equal to T-c. A s ingle peak at V = +/- 60 mV, ascribed to a gap feature, has been obser ved in the conductance spectra at 42 K from which a ratio of 2 Delta(0 )/KBTC = 6.2 (+/- 0.5) is obtained. The temperature dependence of Delt a is compared with the BCS theory. Alternative non-BCS mechanisms may also have to be invoked to obtain satisfactory agreement between the m easured values and theory. Attempts to fit the experimental data by co nsidering lifetime smearing Dynes model have resulted in Delta = 25 me V and Gamma = 4.1 meV.