Tunneling Center as a Source of Voltage Rectification in Josephson Junctions

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Abstract
A novel mechanism of fluctuation-induced voltage rectification in a Josephson junction is analyzed. A point contact with a defect tunneling incoherently between two states is proposed as a source of nonthermal fluctuations which produce asymmetric dichotomic noise. The dc current-voltage characteristics are calculated, and several transport regimes are identified according to the frequency, amplitude, and asymmetry of the noise. The limiting cases of fast and slow fluctuations are investigated analytically. The loaded dc curves exhibit voltage rectification (nonzero voltage at zero current bias) and pronounced singularities in the differential resistance. The system can be used to measure selected characteristics of the tunneling dynamics.