Nanopatterned base strengthens ultrathin superconducting films
A Swedish-led team says shaping the surface below a cuprate film helped it retain superconductivity at higher temperatures and in stronger magnetic fields.
By Tom Brennan · Health & Medicine Correspondent
3 min read
Researchers in Sweden have reported a way to make an ultrathin superconducting material keep its zero-resistance state under harsher conditions. The result matters because superconductors remain difficult to use in electronics, power systems and quantum devices when heat and magnetic fields disrupt their behavior.
Chalmers University of Technology said the team improved performance by altering the surface beneath the superconducting layer, rather than changing the material’s chemistry. The work was published in Nature Communications under the title “Boosting superconductivity in ultrathin YBa2Cu3O7−δ films via nanofaceted substrates.”
Superconductors can carry electrical current without the energy losses that ordinary conductors release as heat. According to Chalmers, that property could make electronic systems and energy technologies far more efficient, while digital devices, data centers and information and communications networks account for an estimated 6% to 12% of global electricity use.
Why the materials remain hard to deploy
The main barrier is operating conditions. Many superconductors need temperatures around minus 200 degrees Celsius, which requires demanding cooling systems, according to Chalmers.
Magnetism adds a second obstacle. Strong magnetic fields can damage or suppress superconductivity, creating problems for advanced electronics and quantum systems that either produce magnetic fields or depend on them.
The Chalmers-led group worked with a copper-oxide superconductor from the cuprate family. Cuprates already operate at higher temperatures than many other superconductors, but Chalmers said their chemistry is hard to alter after fabrication.
A change below the film
The researchers used a superconducting layer only a few nanometers thick, far thinner than a human hair. Such films are grown on a substrate, a supporting base that influences how atoms arrange themselves during manufacturing.
Before depositing the film, the team treated the substrate in a high-temperature vacuum process. Chalmers said that step produced a regular pattern of nanoscale ridges and valleys on the surface.
Eric Wahlberg of RISE Research Institutes of Sweden, one of the study’s authors, said the atomic structure of the substrate can steer how atoms in the superconducting film settle. By reshaping that surface, the researchers were able to affect the film’s superconducting behavior when temperature and magnetic field strength increased, according to Chalmers.
The conceptual setup described by Chalmers used magnesium oxide as the substrate and YBCO, a yttrium barium copper oxide superconductor, as the top layer. The study’s authors said the patterned interface changed the electronic conditions where the two materials meet.
Floriana Lombardi, a professor of quantum device physics at Chalmers and lead author of the study, said the team observed electron behavior at the interface taking on a preferred direction that helped support the superconducting state. Chalmers said the films remained superconducting at higher temperatures than previously possible and under strong magnetic fields, though the university summary did not give numerical operating thresholds.
A design route for future devices
The findings point to a design strategy based on surface engineering. Chalmers said the approach differs from efforts centered on discovering new superconductors or modifying chemical composition.
Lombardi said the work shows that shaping the substrate can improve superconductivity in existing materials. According to Chalmers, the researchers believe the method could help future superconductors operate at much higher temperatures, potentially closer to room temperature.
The author list includes researchers from Chalmers, RISE, Ca’ Foscari University of Venice, Birla Institute of Technology and Science Pilani, the Indian Institute of Science Education and Research, Uppsala University, Université Grenoble Alpes, Université de Toulouse, INSA-T and BTU Cottbus-Senftenberg. Chalmers said part of the work was done at the Myfab Chalmers cleanroom, with funding from the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the European Union and the Deutsche Forschungsgemeinschaft.
This story draws on original reporting from ScienceDaily.