(a) 3-dim view of wash-board potential in the RSJ model as a function of the phase and of the bias current. The current spans from 0 to Ic . In (b) EJ is half of the value used in (a), and this favors phase diffusion regime (see text). (c) A 2-dim cut from (b) for a fixed value of the current. TA stands for thermal activation (black dotted line), while MQT for macroscopic quantum tunneling (red dotted line). Once the particle/phase overcomes the barrier, it rolls in the running state. Retrapping processes may happen for intermediate levels of dissipation determining a phase diffusion (PD) regime.
Schematic representation of SCD measurements from the thermal regime to macroscopic quantum tunneling.
Switching current probability distribution at H = 0 (a) and H = 6.09 G (b) of a NbN/MgO/NbN JJ (Refs. 62 and 63).
Top frame: temperature dependence of the standard deviation σ of the switching distributions for H = 0 G (squares) and H = 6.09 G (circles) shown in Fig. 3. Bottom frame: a numerical simulation of the data. In the inset escape rates (symbols) as a function of the barrier height at zero magnetic field for temperatures near T* are shown, together with numerical simulations (dashed lines).
Schematic representation of SCD measurements in the case of direct transition from MQT to phase diffusion regime.
Comparison of device parameters.
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