•Roland Schäfer, Bernhard Limbach, Peter vom Stein und Christoph
Wallisser
Forschungszentrum Karlsruhe, Institut für Festkörperphysik,
Postfach 3640, 76021 Karlsruhe
We report measurements on single electron pumps consisting of two metallic
islands formed by three tunnel junctions in a row. We focus on the linear
response conductance as a function of gate voltages and temperature of
three samples with varying system parameters. In all cases strong quantum
fluctuation phenomena are observed by a log(kBT/(2Eco))-reduction
of the maximal conductance where Eco measures the coupling strength
between the islands. The samples display a rich phenomenology culminating
in a non-monotonic behavior of the maximal conductance as a function of
temperature.