In a groundbreaking study published in the journal *Science, Technology and Advanced Materials* (translated from Japanese as *Kōgaku*, *Gijutsu to Zairyō*), researchers have uncovered a potential unified explanation for a long-debated phenomenon in superconductors. The spontaneous Hall effect (SHE), a voltage that appears perpendicular to an electric current in zero magnetic field, has been observed in both conventional and unconventional superconductors. This effect, which manifests as a peak near the superconducting transition temperature, has puzzled scientists for years, with theories ranging from intrinsic mechanisms like spontaneous symmetry breaking to extrinsic factors such as material inhomogeneities.
Led by Nadia Stegani of the University of Genoa in Italy, the research team conducted an experimental study focusing on two distinct types of superconductors: conventional, low-transition temperature (Tc) niobium (Nb) and unconventional, intermediate-Tc iron selenide-telluride (Fe(Se,Te)). Their findings revealed distinct SHE peaks around the superconducting transition, with variations in height, sign, and shape. These variations suggest a common underlying mechanism that transcends the specific material properties.
“We observed that the spontaneous Hall effect appears as a peak near the superconducting transition temperature in both types of superconductors,” Stegani explained. “This indicates that there might be a universal mechanism at play, independent of the material’s specific characteristics.”
The researchers propose that spatial inhomogeneities in the critical temperature, caused by local chemical composition variations, disorder, or other forms of electronic spatial inhomogeneities, could be the key to understanding the SHE. To support this hypothesis, they conducted comprehensive finite element simulations of randomly distributed Tc values, varying the Tc distribution, spatial scale of disorder, and amplitude of the superconducting transition.
“The comparison between our experimental results and simulations suggests a unified origin for the SHE in different superconductors,” Stegani added. “Different phenomenology can be explained in terms of the amplitude of the transition temperature in respect to the Tc distribution.”
This research has significant implications for the energy sector, particularly in the development of more efficient and reliable superconducting materials. Understanding the origin of the SHE could lead to advancements in the design and optimization of superconductors for various applications, including energy transmission, medical imaging, and high-speed transportation.
As the world continues to seek innovative solutions for sustainable energy, the insights gained from this study could pave the way for breakthroughs in superconducting technology. By unraveling the mysteries of the spontaneous Hall effect, researchers are not only deepening our understanding of fundamental physics but also opening new avenues for technological innovation.
“Our findings provide a crucial step towards a unified understanding of the spontaneous Hall effect in superconductors,” Stegani concluded. “This could have far-reaching implications for the development of next-generation superconducting materials and devices.”