Control of Coulomb blockade in a mesoscopic Josephson junction using single electron tunneling

Abstract

We study a circuit where a mesoscopic Josephson junction ͑JJ͒ is embedded in an environment consisting of a large bias resistor and a normal-insulator-superconductor ͑NIS͒ junction. The effective Coulomb blockade of the JJ can be controlled by the tunneling current through the NIS junction leading to transistor-like characteristics. We show using phase correlation theory and numerical simulations that substantial current gain with low current noise (i n Շ1 fA/ͱHz) and noise temperature ͑Շ0.1 K͒ can be achieved. Good agreement between our numerical simulations and experimental results is obtained.

Dynamics of Bloch oscillating transistor near the bifurcation threshold

“…The normal and inverted operation regions are defined by sign combinations (V C , I E , −I B ) and (V C , I E , I B ), respectively. 9 Both the normal and inverted modes of operation display a strong increase in the onset of the LZ tunneling current, which is seen as the movement of the shoulders in the I V curves up to larger currents. The down-turning shoulders in the upper and lower sets of the I V curves are distinct features of LZ tunneling, 13 while the data at I B = 0 display only smeared bumps of these features.…”

“…In our numerical analysis, we have considered the circuit model used by Hassel et al 9 and modified it for current bias configuration. Here, we have calculated the island charge as a function of time by taking into account three contributions: charge relaxation through R C together with the tunnel current through the emitter and base junctions, respectively.…”

“…The tunnel currents through these junctions are calculated using time-dependent P (E) theory. 9 In the simulation, P (E) is calculated numerically by considering only the real part of the environmental impedance. The simulation runtime was chosen longer than the time constant due to R B and the capacitance from base to ground so that the steady state was reached properly.…”

“…Above the threshold, two possible dynamical steady-state solutions emerge at fixed I B . 9 The existence of a bifurcation point is important as, with proper design, the vicinity of such a point can be employed to improve the characteristics of the BOT. In this paper, we investigate experimentally the bifurcation threshold in the BOT, and demonstrate current-gain enhancement for small-E J -device operation as the threshold is approached.…”

Superconductor-Metal Transition in an Ultrasmall Josephson Junction Biased by a Noisy Voltage Source

“…This approach called ''the time-dependent PE theory'' has already been used in previous numerical simulations [22]. The approach is justified for the high-impedance environment 1, but is not valid in the opposite case of the low-impedance environment < 1 (see below).…”