Practical applications of superconductors, both in large-scale devices or highly sensitive superconducting electronics is limited by the presence of vortices (quantized magnetic flux lines), whose movements result in losses, internal noise, and reduced performances. The conventional strategy to overcome the flow of vortices within a superconducting material is to pin them along artificial defects.
This research provides a novel avenue toward achieving unprecedentedly high values of the critical current density at high field and temperatures, in high temperature superconducting nanowires by tailoring the material geometry, preventing vortex penetration. We have theoretically and experimentally demonstrated that by reducing the width, W, of nanowire-patterned high temperature superconducting films, the first penetration field, Hc1, below which no vortices are present, is extended up to very large applied field values, on the order of∼1 T. Tailored nanowires show a basically temperature-independent critical current density values, approaching the superconducting depairing limit, well above the values achieved using conventional flux pinning strategies.
Our results may have important consequences in practical applications. On the one hand, the fact that no vortices are present in the nanowires makes them excellent candidates to be used in noise-sensitive sensors or quantum systems. On the other hand, the very large values of current density achieved at high applied fields and temperatures may be also relevant at large scale, with potential to improve the performance of actual thin strips.
Depairing Current at High Magnetic Fields in Vortex-Free High-Temperature Superconducting Nanowires
Víctor Rouco, Carles Navau, Núria Del-Valle, Davide Massarotti, Gian Paolo Papari, Daniela Stornaiuolo, Xavier Obradors, Teresa Puig, Francesco Tafuri, Álvaro Sanchez, Anna Palau
NanoLetters 19, 4174-4179, 2019
Figure: (a) False colour top-view (top) and cross-sectional (bottom) SEM image of 80 nm-wide, 150 nm-thick nanowire. (b) First penetration field, Hc1, as a function of the nanowire width, W. Inset figures depict the aspect ratio of different nanowires