Easy Vortex Motion in an Artificial Channel of YBa₂Cu₃O_7-δSuperconducting Films

Abstract

Quasi-Josephson effect produced by a coherent vortex motion in the horizontal part of the laser-performed Π-shaped channel of a YBa2Cu3O 7−δ superconducting bridge was investigated by means of electric transport measurements. We observed that in our structures, in a limited range of temperatures and bias currents, the vortices were confined in the channel only and moved coherently with the velocity of 3 × 10 4 m/s. The corresponding current-voltage characteristics of the bridge exhibited Josephson-like voltage steps with the amplitude dependent on temperature, but independent of the bias current.

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

“…Our atomic force microscopy (AFM) and scanning tunneling microscopy (STM) (see Fig. 1) analysis confirmed that channel's material was of lower electric conductivity and of lower critical magnetic field H c1 [4,6]. Thus, at temperature T = 88.2 K < T c and biasing current I ≥ 10µA ≈ I c (curve 2, Fig.…”

“…2, curve 1). Increasing temperature, the I 40 decreases exhibiting two linear slopes, both crossing at temperature T ≈ 86.8 K, which was prior to our work determined as the zero-resistance critical temperature of the channel material: T c0 = 86.7 K [4,6]. Presence of two slopes in the I 40 (T ) dependence indicates that the vortex number in the channel vs. temperature dependence N (T ) in our YBCO microbridge with the LW channel is determined by two different physical processes.…”

“…Assuming that creation of additional flux lines in the channel area of our device gives additional voltage steps on the I-V curve [6], the number of vortex-antivortex pairs N in the channel can be estimated from ratio of the current dissipation in vicinity of the n-th and n-th + m step. At a given biasing current and temperature of the superconductor, N = U/U st , where U is the experimentally measured voltage on the I-V dependence at a given temperature (Fig.…”

“…The "voltage height" of the step U st at a given temperature does not depend on biasing conditions, e.g. at T = 87.5 K the averaged U st ≈ 7.8 µV remains constant when biasing current increases as much as 4 times [6]. This work investigates the dependence of the density of the Abrikosov magnetic vortices moving along the LW channel of the superconducting YBCO device vs. its temperature and biasing conditions.…”

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

“…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].…”