Phase dynamics in the tilted periodic potential U: thermal (TA) (green dashed curve) and quantum (MQT) (red dashed curve) escapes are shown in the ideal case of very low dissipation (Q ≫ 1) (a). In the MDR (1< Q < 5) the MQT rate is significantly affected by dissipation (see Eq. (3) ) and retrapping processes in subsequent potential wells become relevant, giving rise to the PD regime (b).
Switching current histograms as function of temperature measured on sample A for H = 0 (a) and H = 12 G (b), respectively. Above the crossover temperature T cr (T cr ∼ 140 mK in (a) and T cr ∼ 120 mK in (b)), the histograms become narrower, rather than wider, and become more symmetric, thereby confirming the importance of retrapping processes in this case.
The temperature dependence of σ in the SCDs measured for sample B. The light grey solid curve (1) is the result of Monte Carlo simulations in the diffusive regime with a quality factor Q = 1.3, while the blue line (2) indicates the saturation level of σ below T cr. The inset shows temperature dependent data for sample A at H = 0 and H = 12 G. The black lines (3,4) indicate the average values of σ in the MQT regime and the value of T cr, which are both reduced by applying a magnetic field (a). Experimental escape rates Γ of sample A as functions of switching current. In the inset, the temperature dependence of the skewness γ is shown for H = 0 and H = 12 G. In the PD regime, retrapping processes cause a progressive bending of Γ and symmetrizing of the switching histograms, as indicated by the temperature dependence of γ (b).
A (Q, kBT/EJ ) phase diagram. The black curve (1) indicates the transition between the TA and PD regimes, which has been extrapolated using Monte Carlo simulations. The labelled points refer to papers works reported in literature. The good agreement between experiments and simulations demonstrates the universal character of the phase diagram. The inset shows the temperature behavior of σ obtained by numerical simulations based on different values of Q. The red line (2) indicates the canonical temperature dependence (TA) of σ. The transition temperature T* and the form of σ in the PD regime are both affected by the junction quality factor Q.
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