Electronic Cooling in Nb/AlO/Al/AlO/Nb Double Tunnel Junctions
Several recent papers have predicted the feasibility of superconducting tunnel junction-based electronic cryocooler devices operating in the temperature range 0.1 - 4K. We have extended previous work in stacked Nb/AlO x devices to investigate the nonequilibrium effects in them and to examine the influence of barrier conductance and layer thickness on the electronic cooling achievable by this technique. We have also analysed the maximum cooling possible with junctions of our present conductance. I. INTRODUCTION Under certain conditions, significant electronic cooling can be achieved in the operation of superconducting tunnel junction based devices . Such an effect has been observed both indirectly via gap-enhancement in double junction SINIS  and directly in single junction SINS  configurations. In order to utilise such cryocoolers for practical applications, it is necessary to optimise the design for maximum cooling efficacy. To do this a detailed understanding of the phy..