Noise-stabilised chaotic substructure on the I–V staircase curve of a rocked superconducting Josephson junction

We investigate the dynamics of a quasiperiodically rocked underdamped Josephson junction in an asymmetric “ratchet” potential, which is irradiated by a weak quasiperiodic field of two frequencies ω1 and ω2. The parameter dependence of the onset of chaos which manifests as irregular substructure in the form of “spiky” tails on the voltage-current characteristics of the junction is investigated. For damping parameter β = 20 and considerable amplitudes α1 = α2 = 0.051 with field frequencies ω1 = 1 and ω2 = 0.005, the calculations demonstrate that this complex substructure is observed at temperature T = 0 K, and dramatically retained in the presence of solely thermal “white” noise, contrary to what would otherwise round the irregular structure and smooth out the features.