title: Shapiro step response in the coherent Josephson flux flow state of Bi2Sr2CaCu2O8+delta.
abstract: We report the first observation of Shapiro steps in the Josephson flux flow state of Bi2Sr2CaCu2O8+delta stacked junctions. When the junction is irradiated at microwave frequencies in a strong parallel magnetic field ( H> or =1 T), a steep increase of the current is observed in the dc current-voltage characteristics when the external microwave frequency and the Josephson frequency are harmonically related. The existence of Shapiro steps in the Josephson flux flow state is strong evidence of coherent motion of the Josephson vortex lattice through the whole thickness of the stack.
authors.affiliation: Research Institute of Electrical Communications, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Y I
authors.initials: YI
authors.lastname: Latyshev
authors.forename: M B
authors.initials: MB
authors.lastname: Gaifullin
authors.forename: T
authors.initials: T
authors.lastname: Yamashita
authors.forename: M
authors.initials: M
authors.lastname: Machida
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuda