Nonuniversality in quantum wires with off-diagonal disorder: a geometric point of view

It is shown that, in the scaling regime, transport properties of quantum wires with off-diagonal disorder are described by a family of scaling equations that depend on two parameters: the mean free path and an additional continuous parameter. The existing scaling equation for quantum wires with off-diagonal disorder [Brouwer et al., Phys. Rev. Lett. 81 (1998) 862] is a special point in this family. Both parameters depend on the details of the microscopic model. Since there are two parameters involved, instead of only one, localization in a wire with off-diagonal disorder is not universal. We take a geometric point of view and show that this non-universality follows from the fact that the group of transfer matrices is not semi-simple. Our results are illustrated with numerical simulations for a tight-binding model with random hopping amplitudes. (C) 2000 Elsevier Science B.V. All rights reserved.