Aspects of dissipation effects on the supercurrent decay of Josephson systems

The effect of the voltage-dependent junction resistance R _j on the critical current decay of Josephson junctions was studied. In the thermal regime, the author has obtained a simple expression for the lifetime of the zero-voltage state which takes into account the nonlinear dependence of R_j on the voltage, removing an assumption of the resistivity shunted junction model (RSJ), which assumes an ohmic shunt resistance to describe the junction dissipation. These results are confirmed by experimental data which also show the relevance of the intrinsic dissipation due to the presence of quasiparticles. This latter aspect is relevant, because it allows extremely underdamped systems to be obtained at low temperatures. These conditions are particularly interesting to study a macroscopic quantum aspect, namely the effects of the presence of quantized energy levels on the supercurrent decay. The dependence of this latter effect on the junction resistance is also briefly discussed