Coherent magnetic vortex motion in optically formed channels for easy flow in YBa2Cu3O72-x superconducting thin films

Abstract

We report our results of investigation of electric and magnetic properties of partially oxygen-depleted channels for easy vortex motion in YBa2Cu3O7-x (YBCO) superconducting, 50-lm-wide, and 100-lm-long microbridges at temperatures below the onset of the superconducting state critical temperature Tc on. The channels were produced by means of a laser-writing technique. The writing was performed using a 0.1–0.3 W power, continuous- wave laser radiation focused down to a * 5 lm spot on the surface of a superconducting film in a nitrogen gas atmosphere, and resulted in perpendicular stripes (channels) with partial (x * 0.2) reduction of the oxygen content in the YBCO stripe. The oxygen-depleted channels exhibit a depressed Tc and lower both the critical current density and the first critical magnetic field, as compared with the laser-untreated areas. The bias current applied to the bridge self-produced a magnetic flux that penetrated the channels in a form of Abrikosov magnetic vortices that, subsequently, moved coherently (a quasi-Josephson effect) along the channels in the narrow temperature range of 0.943 Tc on–0.98 Tc on and manifested themselves as steps on the current–voltage characteristics of our microbridges. Our results demonstrate that laser-induced formation of artificial channels of the flux flow can be used for a precise control of vortex nucleation and their coherent motion in pre-assigned regions of thin-film YBCO devices.