H. S. Knowles, V. F. Maisi, J. P. Pekola
We investigate the influence of quasiparticles on the performance of a hybrid electron turnstile. The device is used to directly probe the density of quasiparticles and monitor their relaxation into normal metal traps. We compare different trap geometries and reach quasiparticle densities below 3 um^-3 for pumping frequencies of 20 MHz. Our data show that quasiparticles are excited both by the device operation itself and by the electromagnetic environment of the sample. Our observations can be modelled on a quantitative level with a sequential tunneling model and a simple diffusion equation.
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http://arxiv.org/abs/1204.1028
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