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Low-energy fixed points of random Heisenberg models

Y. -C. Lin·R. Mélin·H. Rieger·F. Iglói
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Abstract

The effect of quenched disorder on the low-energy and low-temperature properties of various two- and three-dimensional Heisenberg models is studied by a numerical strong disorder renormalization group method. For strong enough disorder we have identified two relevant fixed points, in which the gap exponent, omega, describing the low-energy tail of the gap distribution, P(Delta) ~ Delta^omega is independent of disorder, the strength of couplings and the value of the spin. The dynamical behavior of non-frustrated random antiferromagnetic models is controlled by a singlet-like fixed point, whereas for frustrated models the fixed point corresponds to a large spin formation and the gap exponent is given by omega ~ 0. Another type of universality classes is observed at quantum critical points and in dimerized phases but no infinite randomness behavior is found, in contrast to one-dimensional models.

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Y. -C. Lin, R. Mélin, H. Rieger, F. Iglói. 2003-02-27. Low-energy fixed points of random Heisenberg models. https://doi.org/10.1103/physrevb.68.024424

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