THE OBSERVATION OF NONINTEGRAL SHAPIRO STEPS OF A HIGH-TC SUPERCONDUCTING DC SQUID

An unusual oscillatory behavior of the magnitude of non-integral Shapi ro steps versus applied magnetic fields was observed, on a bi-epitaxia l de SQUID, illuminated by a microwave source. Preliminary results sug gest that the expected position of the first Shapiro step was splitted into two steps; one is larger, while the other smaller than the magni tude of the expected step. A proposed reason for the observation of no nintegral steps is attributed to the possible existence of a finite re sistance, connected in series to one of the single Josephson junctions , in the asymmetric de SQUID circuitry, causing a splitting effect of the Shapiro steps.