A systematic investigation was made of direct-current and alternating-current Josephson effects in MgB2/Nb point-contacts. The observed I–V characteristics of the point-contacts could be described by resistively shunted junction models, and characteristic voltages of 2 to 3mV were obtained. The dependence of the Josephson current step-heights upon the microwave current amplitude could also be fitted by both direct-current and alternating-current biased resistively shunted junction models. The measured temperature dependence of the Josephson critical current agreed well with the Ambegaokar-Baratoff equation at low temperatures, but there were deviations at high temperatures. These results implied that the 39K material was more likely to be a BCS superconductor.

Josephson Effects in MgB2/Nb Point-Contacts. Z.Z.Li, Y.Xuan, H.J.Tao, Z.A.Ren, G.C.Che, B.R.Zhao, Z.X.Zhao: Superconductor Science and Technology, 2001, 14, 944-7