Investigation of vortex density in laser-written pi shaped channel of YBCO bridge by means of I–V dependences

Abstract

A current-self-induced magnetic field Hj , such that Hc1 < Hj < Hc2 at T < Tc, penetrates a thin-film, type-II superconductor forming the Abrikosov magnetic vortex–antivortex pairs in the film’s areas of weakest superconductivity. Our atomic force microscopy and scanning tunneling microscopy images confirm that in 50 ¹m wide, 100 ¹m long and 0.3 ¹m thick YBa2Cu3O7¡x superconducting devices magnetic flux penetrates first into a 5 ¹m wide, ¦-shaped and partially deoxygenated (x ¼ 0:2) channel for easy vortex motion. When the Lorentz force overcomes pinning force in the channel, the flux starts to move and its drift dissipates energy inducing dc voltage. This work reports on the density of coherently moving vortices along the channel vs. temperature in range from 0:93Tc to 0:97Tc. Our simulations show that the vortex density vs. temperature dependence extracted from I–V measurements of our devices follows the temperature dependence of magnetic field penetration depth and the coherence length of the superconductor.