title: Superconducting atomic contacts under microwave irradiation.
abstract: We have measured the effect of microwave irradiation on the dc current-voltage characteristics of superconducting atomic contacts. The interaction of the external field with the ac supercurrents leads to replicas of the supercurrent peak, the well-known Shapiro resonances. The observation of supplementary fractional resonances for contacts containing highly transmitting conduction channels reveals their nonsinusoidal current-phase relation. The resonances sit on a background current which is itself deeply modified, as a result of photon-assisted multiple Andreev reflections. The results provide firm support for the full quantum theory of transport between two superconductors based on the concept of Andreev bound states.
authors.affiliation: Quantronics Group, Service de Physique de l'Etat Condensé (CNRS URA 2464), DSM/DRECAM, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Chauvin
authors.forename: P
authors.initials: P
authors.lastname: vom Stein
authors.forename: H
authors.initials: H
authors.lastname: Pothier
authors.forename: P
authors.initials: P
authors.lastname: Joyez
authors.forename: M E
authors.initials: ME
authors.lastname: Huber
authors.forename: D
authors.initials: D
authors.lastname: Esteve
authors.forename: C
authors.initials: C
authors.lastname: Urbina