Current-Voltage Dependences of YBa2Cu3O7-δ Superconducting Thin Films with Laser-Written Channel of Easy Vortex Motion

Abstract

YBa2Cu3O7-δ superconducting bridges containing laser-performed single, Π-shaped channel have been investigated at temperatures below the material's critical temperature Tc by means of electronic transport measurements. It has been shown that the coherent vortex motion confined in a channel’s Π-shaped horizontal-part of the superconducting bridge might be affected by the thermal unbinding of vortex-antivortex pairs (Kosterlitz-Thouless-Berezinskii phase transition). The coherent vortex motion was observed as the Josephson-like voltage “steps” in the nonlinear current-voltage dependences in a limited range of temperatures, bias currents, and the external magnetic fields. The amplitude of the voltage steps did not depend on the above listed experimental conditions. However, the number of vortex-antivortex pairs, their mutual interaction and ordering depended on the bias current, temperature, and the amplitude of the external magnetic field. Our experimental data, as well as relevant calculations are presented and discussed.