Current-driven vortex dynamics in a periodic potential

Abstract

Quasi-Josephson effects due to coherent vortex motion in artificial reversible periodic potential structures in high-T c superconducting thin films have been investigated. Periodic pinning conditions have been created by applying a magnetic tape containing a prerecorded harmonic signal to the surface of high quality Y 1 Ba 2 Cu 3 O 7Ϫ␦ thin films. Application of the periodic pinning enforces coherence in current-driven motion of Abrikosov vortices in wide and short macrobridges and leads to the appearance of Josephson-like effects manifesting themselves in series of self-induced current steps on the current-voltage characteristics. The equation of motion for vortices flowing across periodic potential structures is analogous to the phase equation for low-capacitance classical Josephson junctions. The perturbation solutions of this equation contain resonant Shapiro-like self-steps resulting from the locking of the frequency at which vortices are created at the sample borders to the resonant frequencies of the vortex system. Self-resonant frequencies are set by the characteristic time of flight across the sample width and across the period of the applied potential. Voltages of the selfinduced current steps have been found to scale with inverse of the characteristic length corresponding to the magnetic period and/or to the sample half-width, consistently with the theoretically derived relations. Experimental data indicate that vortices move in large bundles containing several thousands of flux quanta. The temperature dependence of the step voltages can be ascribed to changes in vortex velocity due to the temperature-dependent viscosity factor. ͓S0163-1829͑99͒01334-X͔

Easy Vortex Motion in an Artificial Channel of YBa2Cu3O7-δSuperconducting Films

“…Current-driven vortices move coherently when they are tightly squeezed and strongly interact between themselves [1], or when they interact with a spatiallyperiodic pinning landscape [2]. Josephson-like effects are the hallmark of the coherent vortex motion.…”

Investigation Details of Vortex Density in Laser-Written Π-Shaped Channel of YBCO Bridge by Means of I-V Dependences

“…The steps appear at voltages for which inverse of the time of flight of flux line matches the frequency of its nucleation [3].…”

Current Distribution in Y-Ba-Cu-O Superconducting Microbridges Containing Π-Shaped Channel for Easy Vortex Motion

“…The force F p depends on the homogeneity of the superconducting thin film's composition [2], structure [3], and geometry (e.g., thickness and/or width) [4]. Thus, F p can be modified * corresponding author; e-mail: arturas.jukna@vgtu.lt using various methods: an introduction of columnar defects into the superconducting film [3], local variations in film's thickness or in chemical composition [2,4], introduction of periodic magnetic barriers [5], etc. Recently, authors in Ref.…”

“…J = J c ), the vortices/antivortices start to move towards the film's center where they annihilate. Flux drift dissipates energy is the critical temperature of the laser untreated superconductor) [5,6,9]. In the presence of microwave (MW) irradiated microbridges, the steps on I-V dependences appear at voltages at which the inverse of the vortex time of flight across the bridge coincides with one of the harmonics of the incident MW frequency [8].…”

“…In the presence of microwave (MW) irradiated microbridges, the steps on I-V dependences appear at voltages at which the inverse of the vortex time of flight across the bridge coincides with one of the harmonics of the incident MW frequency [8]. For MW non-radiated microbridges, these steps appear at voltages for which the inverse of the time of flight of flux line matches the frequency of its nucleation [5].…”