Disorder-induced quantum-Griffiths-like features from a non-conventional renormalization group analysis near four dimensions

摘要

We investigate the role played by symmetry conserving quenched disorder on quantum criticality of a variety of d-dimensional systems with a continuous symmetry order parameter. We employ a non-standard procedure which combines a preliminary reduction to an effective classical random problem and a successive conventional renormalization group treatment. Solving the effective flow equations to first order in epsilon = 4 - d and then restoring the original coupling parameters, for d < 4 we find a quantum critical point scenario exhibiting unusual features, which remind us of some predictions of the quantum Griffiths phase model. (C) 2009 Elsevier B.V. All rights reserved.