The anisotropic Kondo necklace model

A real-space renormalization-group approach is used to investigate the zero temperature phase diagram of the Kondo necklace (KN) model in the presence of an Ising-like anisotropy parameter (δ). In the full anisotropic case, δ=1, this approach yields a quantum critical point (QCP) separating an antiferromagnetic from a non-magnetic, Kondo-like, phase. The critical frontier of the phase diagram is presented as a function of the ratio between the coupling and the bandwith (J/W), and the anisotropic parameter (δ). We find for the KN model that a critical value δc of the anisotropy is required for the appearance of long range magnetic order at zero temperature.