Strong-disorder renormalization-group method on fractal lattices: Heisenberg models and magnetoresistive effects in tight-binding models

R. Mélin, B. Douçot, F. Iglói
2005 Physical Review B  
We use a numerical implementation of the strong disorder renormalization group (RG) method to study the low-energy fixed points of random Heisenberg and tight-binding models on different types of fractal lattices. For the Heisenberg model new types of infinite disorder and strong disorder fixed points are found. For the tight-binding model we add an orbital magnetic field and use both diagonal and off-diagonal disorder. For this model besides the gap spectra we study also the fraction of frozen
more » ... fraction of frozen sites, the correlation function, the persistent current and the two-terminal current. The lattices with an even number of sites around each elementary plaquette show a dominant ϕ_0=h/e periodicity. The lattices with an odd number of sites around each elementary plaquette show a dominant ϕ_0/2 periodicity at vanishing diagonal disorder, with a positive weak localization-like magnetoconductance at infinite disorder fixed points. The magnetoconductance with both diagonal and off-diagonal disorder depends on the symmetry of the distribution of on-site energies.
doi:10.1103/physrevb.72.024205 fatcat:iuwdclttl5c3zjkfumtuozojn4