title: Josephson effect in MgB(2) break junctions.
abstract: We present the first observation of the dc and ac Josephson effect in MgB(2) break junctions. The junctions, obtained at 4.2 K in high-quality, high-density polycrystalline metallic MgB(2) samples, show a nonhysteretic dc Josephson effect. By irradiating the junctions with microwaves we observe clear Shapiro steps spaced by the ideal Delta V value. The temperature dependence of the dc Josephson current and the dependence of the height of the steps on the microwave power are obtained. These results directly prove the existence of pairs with charge 2e in MgB(2) and give evidence of the superconductor-normal metal-superconductor weak link character of these junctions.
authors.affiliation: INFM-Dipartimento di Fisica, Politecnico di Torino, 10129 Torino, Italy. gonnelli@polito.it
authors.forename: R S
authors.initials: RS
authors.lastname: Gonnelli
authors.forename: A
authors.initials: A
authors.lastname: Calzolari
authors.forename: D
authors.initials: D
authors.lastname: Daghero
authors.forename: G A
authors.initials: GA
authors.lastname: Ummarino
authors.forename: V A
authors.initials: VA
authors.lastname: Stepanov
authors.forename: G
authors.initials: G
authors.lastname: Giunchi
authors.forename: S
authors.initials: S
authors.lastname: Ceresara
authors.forename: G
authors.initials: G
authors.lastname: Ripamonti