Riccardo Arpaia

A new international study involving Ca’ Foscari University of Venice, carried out in close collaboration with Chalmers University of Technology (Göteborg, Sweden) and other research partners, has identified a powerful new way to strengthen superconductivity in ultrathin copper-oxide films. The work shows that the nanoscale morphology of the substrate on which a superconducting film is grown can actively enhance its properties, leading to a higher superconducting onset temperature and a much stronger resistance to applied magnetic fields. The study, published in Nature Communications, focuses on YBa2Cu3O7-δ (YBCO), one of the most extensively studied high-temperature cuprate superconductors. By combining transport measurements, spectroscopy, structural and morphological characterization, and theoretical modelling, the researchers demonstrate that the interface between the film and the substrate can be engineered as an effective tool to manipulate the electronic ground state of the material.   A new route to control cuprate superconductors Unlike many two-dimensional materials, cuprates cannot be easily tuned after growth. Their carrier density is largely fixed during synthesis, and conventional electrostatic gating is generally ineffective. For this reason, finding alternative ways to control their properties remains a central challenge in the field. In this work, the researchers show that one such route lies in the substrate itself. Before film deposition, the surface of (110)-oriented MgO is thermally reconstructed, producing a quasi-periodic landscape of nanofacets with ridges and valleys on the nanometer scale. When YBCO is grown on this textured surface, the interface induces an additional electronic potential that has a profound impact on the superconducting state.   Stronger superconductivity in ultrathin films The most remarkable effects emerge in the thinnest films. Compared with 50 nm samples, 10 nm YBCO films grown on the nanofaceted substrate display a superconducting onset temperature more than 15 K higher and an upper critical field enhanced by more than 50 tesla. For Riccardo Arpaia, researcher at Ca’ Foscari, the result is especially meaningful because it builds on a materials platform that has been studied for many years: “These YBCO films on MgO have been part of our research journey since the very beginning of my PhD, around fifteen years ago, and they have never stopped surprising us. But this result goes beyond expectations: seeing a critical temperature higher than in the bulk material, and understanding that this originates from the growth dynamics we induced at the interface, shows that we can genuinely learn to manipulate materials in increasingly precise ways to obtain stronger superconducting properties.”   When the substrate becomes an active element According to the combined experimental and theoretical analysis, the enhancement is linked to the emergence of an interfacial electronic order involving electronic nematicity and unidirectional charge density waves, both promoted by the specific nanoscale texture of the substrate. Rather than acting as a passive support, the substrate becomes an active element that reshapes the electronic landscape of the film and stabilizes stronger superconductivity. This is one of the most significant aspects of the study: it suggests that the performance of complex quantum materials may be improved not only through chemistry, but also through the deliberate design of interfaces and surface morphology.   A broader perspective for quantum materials research For Ca’ Foscari, the study highlights the importance of international and interdisciplinary research on superconductivity and quantum materials, as well as the value of long-term collaborations capable of integrating materials growth, advanced characterization and theory. More broadly, the findings point to a new paradigm for superconductor design. Instead of improving performance only by modifying composition, it may be possible to enhance superconducting properties by tailoring the substrate and the interface at the nanoscale. This opens promising perspectives for future high-performance superconducting materials for energy-efficient electronics, high-field magnet technologies and quantum devices.   The full study is published in Nature Communications and is available at https://doi.org/10.1038/s41467-025-67500-2