Crafting vortex topologies into copper-oxide superconductors by focused helium-ion-beam irradiation and their temporal evolution

Description

Electronic devices based on the manipulation of Abrikosov vortices in superconductors require precise fabrication of pinning landscapes, which can evoke guided vortex motion and nonreciprocal electrical transport. Key to this is strong magnetic coupling of vortices, necessitating their spacing within the London penetration depth. However, achieving nanoscale precision in copper-oxide superconductors is challenging due to their complex atomic structure. To overcome this, we use the focused ion beam of a helium ion microscope (He-FIB) to create densely spaced nanocolumns in thin films, where superconductivity is locally suppressed by pair-breaking resulting from point defects.

The effectiveness of our method is demonstrated by vortex commensurability effects in YBa₂Cu₃O₇₋_δ (YBCO) thin films with an ultradense hexagonal nanopattern, exhibiting critical current maxima in variable magnetic field (matching peaks) at unprecedentedly high fields of 6 T. These effects persist over a broad temperature range, down to 2 K [1]. Notably, quasi-kagomé pinning structures induce nonreciprocal transport effects, paving the way for nonlinear electronic devices. Furthermore, we show that He-FIB patterning can be applied to Bi₂Sr₂CaCu₂O₈_+x thin films, enabling efficient pinning landscapes in this highly anisotropic superconductor.

A critical but underexplored aspect is the temporal stability of He-FIB-created patterns. To address this, we examined YBCO pinning arrays stored at room temperature for nearly six years. After an initial Tc increase over three years, only minor degradation followed. Crucially, vortex-matching signatures remained intact, indicating that room-temperature annealing reduced defect density around the irradiated columns while preserving strong pinning at their cores [2]. These findings underscore the potential of He-FIB-engineered pinning landscapes for advanced fluxonic applications.

References
[1] M. Karrer, B. Aichner, K. Wurster, C. Magén, C. Schmid, R. Hutt, B. Budinská, O.V. Dobrovolskiy, R. Kleiner, W. Lang, E. Goldobin, D. Koelle, Vortex matching at 6 T in YBa2Cu3O7-δ thin films by imprinting a 20-nm periodic pinning array with a focused helium-ion beam, Phys. Rev. Applied 22, 14043 (2024).
[2] S. Keppert, B. Aichner, P. Rohringer, M.-A. Bodea, B. Müller, M. Karrer, R. Kleiner, E. Goldobin, D. Koelle, J.D. Pedarnig, W. Lang, Temporal Evolution of Defects and Related Electric Properties in He-Irradiated YBa2Cu3O7-δ Thin Films, Int. J. Mol. Sci. 25, 7877 (2024).

Acknowledgments
This work was funded by a joint project of the Austrian Science Fund (FWF), grant I4865-N, and the German Research Foundation (DFG), grant KO 1303/16-1, and is based upon work from COST Actions CA21144 (SuperQuMap), CA19108 (Hi-SCALE), CA19140 (FIT4NANO), and CA23134 (PolyTopo), supported by COST (European Cooperation in Science and Technology).

Period	22 Sept 2025
Event title	17th European Conference on Applied Superconductivity
Event type	Conference
Location	Porto, PortugalShow on map
Degree of Recognition	International