Microscopic theory of atomic and electronic stretched exponential relaxation in high temperature superconductors

Measured dimensionless room-temperature conductivity relaxation stretching fractions beta in YBCO are in excellent agreement with theoretical predictions, which in 1995 identified two magic fractions, beta = 3/5 and beta = 3/7. Thus, relaxation studies provide an absolute measure of ``ideality{''} in these complex materials, independent not only of composition x but even of crystal structure. The relaxation stretching fractions beta associated with T-c itself, reported in 2000, are also explained by the magic fraction beta = 3/5 predicted by microscopic theory. One can infer that the interactions responsible for high-temperature superconductivity are short range, non-magnetic, and primarily associated with resonant trapping centers in semiconductive layers. (C) 2000 Elsevier Science B.V. All rights reserved.