Measured Temperature Dependence of the $cos\varphi$ Conductance in Josephson Tunnel Junctions

The temperature dependence of the $cos\varphi$ conductance in Sn-O-Sn Josephson tunnel junctions has been measured just below the critical temperature, $T_c$. From the resonant microwave response at the junction plasma frequency as the temperature is decreased from $T_c$ it is deduced that the amplitude of the $cos\varphi$ term first increases from near zero to positive values and only at $\frac{T}{T_c}\lesssim 0.96$ attains values of order-1.