Fractional Josephson vortices at YBa${}_2$Cu${}_3$O${}_{7-x}$ grain boundaries

Abstract

We report numerical simulations of magnetic flux patterns in asymmetric 45${}^{\circ }$ [001]-tilt grain boundaries in YBa${}_2$Cu${}_3$O${}_{7-x}$ superconducting films. The grain boundaries are treated as Josephson junctions with the critical current density $j_c(x)$ alternating along the junctions. We demonstrate the existence of Josephson vortices with fractional flux quanta for both periodic and random $j_c(x)$. A method is proposed to extract fractional vortices from experimental flux patterns.

4 pages, 4 figures, ReVTeX, submitted to PRL