| Popis: |
Performance and energy consumption of large-scale computing infrastructures could be improved significantly by adoption of superconducting electronics. Rapid single flux quantum (RSFQ) circuits with logic based on the vortex state in Type II superconductors were first demonstrated several decades ago and as of now, research focusing on developing modern superconducting electronic components operating on the level of a single Abrikosov vortex is ongoing, where RSFQ serves as a convenient reference point. The main focus of this project was one crucial aspect for such components, namely reliable manipulation of vortex dynamics under transport current. A set of realistic and relevant micron scale geometries of superconducting thin films with a circular vortex trap were simulated by obtaining numerical solutions of time-dependent Ginzburg-Landau equations in two spatial dimensions. Within the scope of this work, successful manipulation of vortex dynamics means being able to perform each of the following actions on-demand: introduce one vortex into the device, pin it to the trap, remove it from the device. Current and time-dependent behaviour of vortices in different device geometries was studied and an important role of seemingly small changes in geometric parameters was established. Certain geometric configurations were discovered to be inherently more favourable for deterministic control of vortex dynamics, while others were identified as inherently unfavourable. Practically conceivable methods to separate between the two were introduced. Repeated sequences of "write" (trapping a vortex) and "erase" (removing a vortex) operations with square waves of transport current tailored to a particular device geometry were simulated as a demonstration of successful vortex manipulation. Findings of this thesis are expected to improve the success rate of physically conducted experiments within the area of superconducting vortex-based electronics. |
