Scientists at the University of Warwick have found that a copper-based superconductor studied for decades is not structurally uniform, as previously assumed. Using scanning 3D X-ray diffraction at the European Synchrotron Radiation Facility (ESRF) in France, the researchers detected a patchwork of two slightly different atomic arrangements and unexpectedly broad transition zones between them. The finding could require scientists to revisit established theories and measurements of high-temperature superconductivity.
High-temperature superconductivity is a major area of research because superconductors can carry electrical current without resistance, eliminating the energy losses found in conventional materials. Their ability to support extremely powerful magnets could also benefit future power grids, medical scanners and quantum computers.
The University of Warwick team, from the Department of Chemistry and working with the ESRF, studied a copper-based superconductor known as a cuprate, or copper oxide, material. Cuprate superconductors can conduct electricity without resistance at unusually high, although still very low, temperatures compared with other superconductors.
3D imaging reveals hidden crystal structures
For approximately 40 years, theories of cuprate superconductivity have generally been based on the assumption that these materials have the same crystal structure throughout their interiors. The new research indicates that this assumption does not always hold.
The researchers used scanning 3D X-ray diffraction, an imaging technique that reveals how atoms are arranged deep inside a crystal. In principle, the method is similar to a medical CT scan, but it maps atomic structures rather than tissues or organs.
The measurements allowed the team to create detailed three-dimensional images of the superconductor’s interior and identify structural variations that conventional techniques had not revealed.
Rather than a uniform crystal, the researchers found a patchwork of regions with two slightly different atomic arrangements. The boundary between these regions was also hundreds of times wider than expected.
These broad transition zones are not simply narrow divisions between neighboring structures. They are large enough to behave as structures in their own right and may affect how electrical current moves through the material.
Reconsidering long-standing assumptions
Professor Mark Senn, who led the research at the University of Warwick’s Department of Chemistry, said the finding could have a significant effect on superconductivity research.
“For 40 years, the working assumption has been that these materials are the same from start to finish, and almost all theory has been built on that image. We have shown that this does not hold true. The crystals are essentially patchy and textured, with unusually large boundary areas that may work against superconductivity rather than just alongside it.”
“This may explain why some materials perform better than others, and means we will need to reinterpret some of our existing bulk measurements and build future theoretical models that incorporate this structural complexity.”
The findings suggest that internal boundaries may actively interfere with superconductivity rather than simply coexist with it. Hidden structural differences could therefore help explain why some superconducting materials perform better than others.
The results also indicate that earlier experiments, particularly those measuring the overall properties of these materials, may need to be reassessed. Future theories may need to account for the complex internal structure of real crystals instead of treating them as completely homogeneous.
Implications for future superconductors
The researchers suspect that similar hidden structural patterns could be common in other cuprate superconductors. Comparable features may also occur in related materials being studied for their ability to become superconducting under extreme pressures.
Beyond challenging existing theories, the study demonstrates the capabilities of a new generation of imaging technology. The measurements were made possible by the recent €150 million upgrade to the ESRF, which provides extremely powerful X-ray beams for examining materials in detail.
The technique enables scientists to study the three-dimensional interiors of materials with a high level of precision, potentially revealing how hidden atomic structures influence their behavior. In superconductivity research, a better understanding of the relationship between internal crystal structure and electrical performance could help scientists identify ways to improve superconducting materials.
Such advances could support the development of more capable energy systems, powerful magnets, medical imaging devices and quantum technologies.
Source: www.sciencedaily.com