Guided Vortex Motion Control in Superconducting Thin Films by Sawtooth Ion Surface Modification

Abstract

Design of flux profile and guided motion of magnetic flux quanta (also known as vortices) are central issues for functionality of superconducting devices. Anchoring vortex movement by trapping flux lines through the use of defects and preventing vortex entry by shielding magnetic field have been broadly explored, which can also enable reduction of noise for optimal device operation. Removing vortices entirely via the so-called ratchet effect (employing an asymmetric energy potential) is another alternative. This ratcheting potential is also used in DNA splitting, particle separation, surface atom electromigration, and electrophoresis. Utilizing a superconductor with the ratchet vortex pinning potential induces a dominant motion direction, which can be used to pump flux out from device functional zones. In this work, a varying thickness superconductor with its tailored intrinsic pinning mechanism has been simulated and proven to provide this preferential vortex motion. We demonstrate both theoretically and experimentally that a varying thickness superconducting ratchet is indeed possible. Furthermore, the sawtooth shape of the bridge provides a tunability to the preferred vortex motion direction, dependent on the ramp gradient and intrinsic pinning strength.

Vortex control in superconducting Corbino geometry networks

“…The key feature of type II superconductors is the anomalous mixed state where in the presence of magnetic fields normal conducting regions surrounded by persistent circular supercurrents-i.e., vortices-nucleate in the superconducting material and the motion of these vortices without pinning causes electric dissipation [1][2][3]. It is well known that most of the high-T c superconductors are categorized as type II superconductors, and controlling vortices on demand is one of the important prerequisites for creating novel superconducting devices [4][5][6][7].…”