Tunnelling studies in BiSrCaCuO:Pb break junctions

Single-particle tunnelling experiments have been performed on polycrystalline BiSrCaCuO : Pb using break junction configuration in the temperature range 4·2 K ≤ T ≤ Tc. A single peak at V = ± 60 mV, ascribed to a gap feature, has been observed in the conductance spectra at 4·2 K from which a ratio of 2Δ(0)/KBTC = 6·2 (± 0·5) is obtained. The temperature dependence of Δ is compared with the BCS theory. Alternative non-BCS mechanisms may also have to be invoked to obtain satisfactory agreement between the measured values and theory. Attempts to fit the experimental data by considering lifetime smearing Dynes model have resulted in Δ = 25 meV and Γ = 4 ·1 meV.