Using a beam of invisible light, researchers have decoded the magnetic whirlpools that form within superconductors. It can help engineers build more resilient components for power grids, MRI scanners, and particle accelerators.“To improve superconductors, scientists need to understand what vortices contain and how they behave,” said Girsh Blumberg, a distinguished professor of physics and astronomy at Rutgers and co-author of the study, published in Physical Review Letters.Superconductors are celebrated for carrying electric currents with zero resistance. Yet exposure to strong magnetic fields creates microscopic disruptions known as vortices. Inside each vortex, electrical currents swirl around a weakened core where superconductivity breaks down. “It’s like Swiss cheese, with many holes,” added Blumberg.Proving a difficult theoryWhen these vortices shift, the material leaks electrical energy as heat. Physicists have long wanted to peer inside these cores to see how trapped particles behave. Theorists had already predicted that particles inside each vortex would settle into stepped quantum energy levels, much like the rungs of a ladder. However, proving this experimentally has been notoriously difficult because the energy rungs in most materials blur together.To solve the puzzle, the Rutgers team manufactured an iron-based compound containing tellurium and selenium. Using layer-by-layer atomic deposition, professors Seongshik Oh, Hee Taek Yi, and their colleagues created flawless crystalline films just 40 nanometers thick—roughly a thousand times thinner than a human hair. The narrow cores of this compound kept the quantum rungs spaced cleanly apart.The experiments then moved to Tallinn, Estonia, where the films were chilled to minus 438 degrees Fahrenheit under intense magnetic fields. Scientists fired terahertz radiation, a form of low-frequency invisible light, straight through the ultra-thin samples.Testing the two variationsThe team manipulated the polarization of the light beam. Light waves can twist clockwise or counterclockwise as they travel. The researchers discovered that the trapped particles divided cleanly into two distinct groups. One group reacted only to the left-handed spiral, while the other reacted only to the right-handed twist.“That difference allowed the researchers to tell the two groups apart and study each one separately,” noted a press release. “Using their light measurements and mathematical calculations, the researchers estimated the size of the vortices and how long the particles’ responses to light lasted.”“They also estimated how strongly the vortices resist changes in speed or direction and how strong a magnetic field would disrupt superconductivity for each group of particles.”The team also tested two variations of their chemical recipe with different amounts of selenium. Although both samples began superconducting at nearly identical temperatures, their internal mechanics were strikingly different. One recipe produced four times as many particles of the first group as the second, while the other recipe yielded an even split.The results show that superconductors with the same operating temperatures can conceal vastly different internal dynamics. By isolating these trapped particles with polarized light, researchers now have a precise method to fine-tune materials for future heavy-duty electrical technologies.