Role of disorder on the quantum critical point of a model for heavy fermions - art. no. 140402

A zero-temperature real-space renormalization group (RG) approach is used t o investigate the role of disorder near the quantum critical point (QCP) of a Kondo necklace (XY-KN) model. In the pure case this approach yields J(c) =0 implying that any coupling J not equal0 between the local moments and th e conduction electrons leads to a nonmagnetic phase. We also consider an an isotropic version of the model (X-KN), for which there is a quantum phase t ransition at a finite value of the ratio between the coupling and the bandw idth, (J/W). Disorder is introduced either in the on-site interactions or i n the hopping terms. We find that in both cases randomness is irrelevant in the X-KN model, i.e., the disorder induced magnetic-nonmagnetic quantum ph ase transition is controlled by the same exponents of the pure case. Finall y, we show the fixed point distributions P-J(J/W) at the attractors of the disordered, nonmagnetic phases.