LOCALIZATION LENGTH EXPONENT IN QUANTUM PERCOLATION

Connecting perfect one-dimensional leads to sites i and j on the quantum percolation (QP) model, we calculate the transmission coefficient Tij(E) at an energy E near the band center and the averages of ijTij, ijrij2Tij, and ijrij4Tij to tenth order in the concentration p. In three dimensions, all three series diverge at pq=0.36-0.02+0.01, with exponents =0.82-0.15+0.10, +2, and +4. We find =0.380.07, differing from usual Anderson localization and violating the bound 2/d of Chayes et al. [Phys. Rev. Lett. 57, 2999 (1986)]. Thus, QP belongs to a new universality class. © 1995 The American Physical Society.