New type of zero-field steps in the I-V curve of a Josephson junction of intermediate length

We report on the observation of a new type of high-order zero-field steps in the I-V curve of a Josephson transmission line of intermediate length l=L/λJ≊5, where λJ is the Josephson penetration length. On such steps, deviations from the generalized Josephson relation Vdc=N(h/2e)νdet relating the measured dc voltage to the frequency of the radiation emitted from the junction are observed.