Creation and pinning of vortex-antivortex pairs

Computer modeling is reported about the creation and pinning of a magnetic vortex-antivortex (V-AV) pair in a superconducting thin film, due to the magnetic field of a vertical magnetic dipole above the film, and two antidot pins inside the film. For film thickness $=0.1\xi$, $\kappa =2$, and no pins, we find the film carries two V-AV pairs at steady state in the imposed flux range $2.10{\mathrm{\Phi }}_0<{\mathrm{\Phi }}^{+}<3.0{\mathrm{\Phi }}_0$, and no pairs below. With two antidot pins suitably introduced into the film, a single V-AV pair can be stable in the film for ${\mathrm{\Phi }}^{+}\ge 1.3{\mathrm{\Phi }}_0$. At pin separation $\ge 17\xi$, we find the V-AV pair remains pinned after the dipole field is removed, and, so can represent a 1 for a nonvolatile memory.