Number 65 (Story #1), January 24, 1992 by Phillip F. Schewe and Ben Stein|
D-WAVE ELECTRON PAIRS may have been observed in cuprate superconductors. In the BCS theory, superconductivity is thought to come about when electrons pair off into Cooper pairs. The relative orbital angular momentum of the pair can have a value of 0 ("s-wave"), 1 (p-wave), 2 (d-wave), and so forth. Cooper pairs are commonly in s-wave states. In certain "heavy-electron" materials (containing uranium) superconductivity may be p-wave in nature. Now evidence for d-wave superconductivity comes in the form of NMR studies of the copper nuclei in high-temperature superconductivity. In the 3 Feb. issue of Physical Review Letters, three articles are devoted to this subject. A group from the University of Illinois (J. A. Martindale et al.; contact Charles Slichter at 217-333-3834) and a Iowa State/Pavia (Italy) collaboration (Ferdinando Borsa et al.) report experimental results, while a theoretical analysis is presented by Nejut Balut and Douglas Scalapino at UC Santa Barbara.