Temperature dependence of the energy gap in Bi2223 metal oxide superconductor

Spectroscopic studies of the silver-optimum-doped Bi2223 contacts show that the temperature dependence of the parameter Delta follows the BCS curve. However, the tunnel measurements performed for the same series of specimens did not reveal any temperature dependence of the energy gap Delta. The feature observed in the tunnel density of states was retained at temperatures T > T-c, manifesting the presence of the temperature-independent pseudogap E-p. The difference between the data obtained with tunnel spectroscopy and Andreev reflection spectroscopy is explained by the fact that the latter measures the true superconducting energy gap Delta(s)(T), whereas the peaks of the tunneling conductivity are related to the total energy gap Delta of cuprates, which includes both the parameter Delta(s) and the pseudogap E-p: Delta approximate to root Delta(s)(2) + E-p(2). (C) 2000 MAIK "Nauka / Interperiodica".