Figure 1

Schematic of the circuit (upper left inset) and current versus bias and gate voltages (3D plot) showing the checkerboard pattern (right inset) associated with resonant tunneling of Cooper pairs. The contour plot of the right inset is obtained by subtracting the background current thus leaving only the characteristics of the resonant tunneling.Reuse & Permissions

Figure 2

(Color online) (a) Effect of a magnetic field on $IV$ characteristics (current values at different $V_g$’s, showing gate modulation, are superposed): Zero, upper curve; intermediate value, middle curve; complete suppression of the gap of Al, lower curve. (b) The main graph shows the low-bias Coulomb blockade dip: Experimental values (blue), standard BCS Coulomb-blockade thermometry fit (dotted line), and the predictions of the orthodox theory with lifetime broadening and gap inhomogeneity (continuous line). The upper inset shows the conductances for two single Al-Nb junctions of normal resistances $30k\Omega$ (lower curve) and $11k\Omega$ (upper curve).Reuse & Permissions

Figure 3

(Color online) (a) Qualitative comparison between the conductances extracted from the data by averaging out the gate modulation (symbols) and those obtained by numerical simulations (lines) at different magnetic fields. (b) The gap of Al leads (open circle), measured separately, plotted together with the Al gaps determined from the conductance peaks of (a) for three SET samples (square, triangle, and star).Reuse & Permissions