Simulations of Pinned Superconducting Vortices Electrical Responses: Potential Devices

Abstract

Mobile superconducting vortices are quite sensitive to localized disorder that can trap them, a process called pinning. Using various modern patterning techniques one can introduce arrays of artificial pinning sites in thin superconducting films such as holes (empty spaces with various shapes and sizes), or inclusions of a second material such as another superconductor, a normal metal or a ferromagnet. The resulting devices may be useful for low-temperature applications. The time dependent Ginzburg-Landau (TDGL) equations are a powerful tool to simulate the motion of superconducting vortices in such systems. Here, we use the TDGL equations to study the formation and response of vortices in three different environments: (i) external current-induced drift in a square array of circular inclusions of a weaker superconductor, which exhibit both synchronous and asynchronous motions (depending on the applied current); (ii) the current-induced oscillatory (ac) response of pinned vortices, which display a nonlinear inductive response at low frequencies (similar to a Josephson junction); and (iii) tri-stable states (anti-vortex/vortex, no-vortex, vortex/anti-vortex) in a system consisting of two different pinning shapes (circles and triangles).