The effects of microshorts on the properties of Josephson tunnel junctions at a finite dc voltage are studied. The disturbance of the electromagnetic field by microshorts and the resulting dc current-voltage characteristics are calculated assuming the RSJ model for the microshorts. It is shown analytically that a microshort gives rise to a current which does not vanish even at a sufficiently high magnetic field, i.e., an excess current. It is also shown that the amplitude of the excess current depends strongly on the ratio of the microshort resistance to the junction impedance seen from the microshort. The observed magnetic-field dependence of the current-voltage characteristics of junctions showing excess currents is explained well by the present analysis.
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