Anisotropy by design in superconducting Nb thin films via ultrashort-pulse laser irradiation

The ability to fabricate anisotropic superconducting layers à la carte is desired in technologies such as fluxon screening or removal in field-resilient devices, flux lensing in ultra-sensitive sensors, or in templates for imprinting magnetic structures in hybrid magnetic/superconducting multilayers. In this work, laser processing is qualified as an enabling technology in the controllable fabrication of superconducting metasurfaces. Niobium thin films exposed to femtosecond ultraviolet laser pulses exhibit significant changes in their superconducting properties, directly connected with the observed surface topography, crystallite geometry, and lattice parameter modifications. On the mesoscopic scale, quasi-parallel periodic ripple structures (about 260 nm of spatial period) gradually form on the film surface by progressively increasing the laser energy per pulse, E p . This gives way to a stepwise increase of the critical current anisotropy and magnetic flux channeling effects along the ripples. As demonstrated in our resistive and inductive measurements, these superstructures determine the electromagnetic response of the superconducting material. Time-dependent Ginzburg–Landau simulations corroborate the topographical origin of the customized anisotropy. Pulsed laser processing is promoted as a flexible, one-step, and scalable lithography-free technique for versatile surface functionalization in microelectronic superconducting technology. • Laser processing of Nb thin films modifies the lattice and superconducting parameters. • Topography, crystallite geometry, and lattice parameter are modified systematically. • Control over the laser irradiation power allows to customize the induced anisotropy. • Transport measurements disclose the local anisotropy induced by surface topography. • Time-dependent Ginzburg–Landau simulations elucidate the tailored anisotropy.