title: Steps in the negative-differential-conductivity regime of a superconductor.
abstract: Current-voltage characteristics were measured in the mixed state of Y(1)Ba(2)Cu(3)O(7-delta) superconducting films in the regime where flux flow becomes unstable and the differential conductivity dj/dE becomes negative. Under conditions where its negative slope is steep, the j(E) curve develops a pronounced staircase-like pattern. We attribute the steps in j(E) to the formation of a dynamical phase consisting of the successive nucleation of quantized distortions in the local vortex velocity and flux distribution within the moving flux matter.
authors.affiliation: Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208, USA.
authors.forename: M N
authors.initials: MN
authors.lastname: Kunchur
authors.forename: B I
authors.initials: BI
authors.lastname: Ivlev
authors.forename: J M
authors.initials: JM
authors.lastname: Knight