Vortex/Anti-Vortex States in Nano-Patterned Superconducting Films

We model a novel, periodic, thin-film superconducting system containing two differently shaped antidots: circular and equilateral-triangular. In the absence of an external field the system displays two stable states as a function of the applied current: i) a vortex-free state at low current and, ii) above some critical current, a state involving a vortex and anti-vortex pinned to the two respective pinning sites. At still higher currents, the system becomes unstable to repeated nucleation and annihilation of moving vortex/anti-vortex pairs. The two states have distinct inductive responses. It is noted that these properties open the possibility for these systems to be utilized as cryogenic circuit or memory elements.