Scientists at SLAC National Accelerator Laboratory and Stanford University have shown for the first time how high-temperature superconductivity emerges out of magnetism in an iron pnictide, a class of materials with great potential for making devices that conduct electricity with 100 percent efficiency.
In experiments at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL), the team "doped" the material – one of two known types of high-temperature superconductor – by adding or subtracting electrons to enhance its superconducting abilities. Then they used a beam of ultraviolet light to measure changes in the material's electronic behavior as it was chilled to a temperature where superconductivity becomes possible.
The researchers saw the two states battle for dominance: At first the electrons in the material all lined up with their spins pointed in specific directions, a hallmark of magnetism. But as the temperature dropped, a few electrons paired up, like dancers at a party, to effortlessly conduct electricity; then a few more; until finally all the active electrons found partners and the material was fully superconducting, a much more complex behavior.
The results, published April 25 in Nature Communications, are an important step toward understanding how high-temperature superconductors work – information scientists need to realize their dream of engineering superconductors with more useful properties that operate at close to room temperature for a variety of practical applications.