Single electron turnstile and pump devices using long arrays of small tunnel junctions

Abstract

We have investigated, both experimentally and numerically, single electron tunneling devices of interest for current standard applications. The devices consist of long arrays of small tunnel junctions with gate electrodes capacitively coupled to electrodes inside the arrays. Experiments on arrays of 25 small aluminum tunnel junctions with a single gate electrode capacitively coupled to the center of the array (an "array turnstile") have been performed at temperatures down to 40 mK. We observe sharp steps in the I-V characteristics at currents I = ±ef when an rf-signal of frequency f is applied to the gate electrode. The sharp steps can be obtained even without any compensation for background charge. Numerical simulations of a similar device (an "array pump") are also presented. This device consists of an array with two gate electrodes where two rf signals with a phase shift of 90° may be applied. The size of the voltage steps in the I-V characteristics are investigated as a function of several parameters. For instance, the dependence of electrode capacitance, number of junctions, and background charge is investigated.