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Fluxon manipulation by nanoscale artifcial pinning lattices in cuprate superconductors

Subject Area Experimental Condensed Matter Physics
Term from 2020 to 2024
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 442093495
 
Final Report Year 2025

Final Report Abstract

The research project has been exploring new ways to enhance the performance of high-temperature cuprate superconductors, materials capable of conducting electricity without resistance at relatively high temperatures. One primary focus has been on understanding how nanoscopic defects, introduced via helium-ion irradiation, interact with “Abrikosov vortices.” These are tiny current whirlpools that carry one magnetic flux quantum and emerge within superconductors under a strong electric current or in an external magnetic field. Unless these vortices are “pinned” in place, they move and cause energy losses. Therefore, understanding and controlling vortices is a key challenge for practical applications of superconductors. Our approach uses focused helium-ion irradiation to introduce nanoscopic defects in the cuprate superconductor YBa₂Cu₃O₇ (YBCO). By computer simulations of how helium ions collide with atoms in thin YBCO films, we identified the optimal conditions to create tightly packed defect columns. The defects act as effective anchors, or pinning centers, for the vortices. Building on these insights, we applied a focused 30 keV helium-ion beam to produce ultra-dense patterns of pinning sites. Electric transport measurements revealed an unprecedented high commensurability field of 6 Tesla for a triangular defect lattice with only 20 nanometers between sites. This cutting-edge fabrication technology unlocks experimental access to new areas of vortex physics. We proposed an “ordered Bose glass” phase in nanopatterned YBCO films, suggesting that under specific conditions, the vortices arrange themselves into a unique glass-like structure with remarkable properties. Intriguingly, the nanostructured samples exhibited a reentrant zero resistance at high magnetic fields and revealed the theoretically predicted “transverse Meissner effect,” in which the vortex arrangement strongly resists any tilt of the magnetic field. In addition to YBCO, the project has spurred the synthesis and analysis of other high-temperature superconductors, such as the highly anisotropic Bi₂Sr₂CaCu₂O₈₊x (Bi-2212). Detailed measurements revealed its excellent superconducting qualities. Preliminary experiments indicate that nanostructuring by focused helium ion-beam irradiation also applies to Bi-2212 thin films. The outcomes of this research project have direct relevance for applications requiring zero resistance under extreme conditions, such as powerful electromagnets for medical imaging. The advanced techniques for nanostructuring these complex materials are indispensable for manufacturing electronic devices and sensors, possibly extending into quantum technologies. We expect the follow-up research embedded in our network of collaborators will unravel more of the fascinating quantum properties of these remarkable materials.

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