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RESEARCH PRODUCT

Spatially resolved measurement of nonequilibrium quasiparticle relaxation in superconducting Al

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Spatially resolved relaxation of nonequilibrium quasiparticles in a superconductor at ultralow temperatures was experimentally studied. It was found that the quasiparticle injection through a tunnel junction results in the modification of the shape of the I-V characteristic of a remote ``detector'' junction. The effect depends on the temperature, injection current, and proximity to the injector. The phenomena can be understood in terms of the creation of quasiparticle charge and energy disequilibrium characterized by two different length scales ${\ensuremath{\Lambda}}_{{Q}^{*}}~5$ and ${\ensuremath{\Lambda}}_{{T}^{*}}~40$ $\ensuremath{\mu}$m. The findings are in good agreement with existing phenomenological models, while more elaborate microscopic theory is mandatory for a detailed quantitative comparison with the experiment. The results are of fundamental importance for understanding electron transport phenomena in various nanoelectronic circuits.