arXiv:cond-mat/9502061 · Journal of Physics A Mathematical and General
Replica symmetry breaking and the renormalization group theory of the weakly disordered ferromagnet
Виктор Степанович Доценко, D E Feldman
Abstract
We study the critical properties of the weakly disordered p-component ferromagnet in terms of the renormalization group (RG) theory generalized to take into account the replica symmetry breaking (RSB) effects coming from the multiple local minima solutions of the mean-field equations. Recently it has been shown that for p<4 the traditional RG flows at dimensions D=4- epsilon , which are usually considered as describing the disorder-induced universal critical behaviour, are unstable with respect to the RSB potentials as found in spin glasses, and a new type of stable one-step RSB fixed point has been discovered. Here it is demonstrated that for a general type of the Parisi RSB structures there exist no stable fixed points, and the RG flows lead to the strong-coupling regime at the finite scale R * approximately exp(1/u), where u is the small parameter describing the disorder. The physical consequences of the obtained RG solutions are discussed. In particular, we argue that discovered RSB strong-coupling phenomena indicate the onset of a new spin-glass-type critical behaviour in the temperature interval tau < tau * approximately exp(-1/u) near Tr. The possible relevance of the considered RSB effects for the Griffith phase is also discussed.