Number 242 (Story #2), September 28, 1995 by Phillip F. Schewe and Ben Stein SOME MATERIALS MIGHT EXHIBIT TWO KINDS OF SUPERCONDUCTIVITY. At low temperatures electrons in certain materials pair up. The pairs, condensing into a single macroscopic quantum state, constitute a supercurrent which does not lose energy, through interactions with the lattice of atoms forming the material. In low-temperature superconductors the electron pairs are said to be in an "s wave" state, one in which the electrons have no angular momentum relative to each other. Some theorists believe that the pairing mechanism is different in high-temperature cuprate superconductivity and that the pairs exist in a different state called a "d wave." Indeed, recent experiments trying to settle the issue lean toward the d-wave explanation, but the results have not been definitive. Now, K. Alex Muller of IBM proposes that in some materials both kinds of superconductivity may be at work. That is, two types of superconductivity may occur at the same transition temperature in the same material. (K. Alex Muller, Nature, 14 September 1995.)