Study of the 1D anisotropic Kondo necklace model at criticality via an entanglement entropy estimator

We use an estimator of quantum criticality based on the entanglement entropy to discuss the ground state properties of the 1D anisotropic Kondo necklace model. We found that the T=0 phase diagram of the model is described by a critical line separating an antiferromagnetic phase from a Kondo singlet state. Moreover we calculate the conformal anomaly on the critical line and obtained that c tends to 0.5 as the thermodynamic limit is reached. We conclude that these transitions belong to Ising universality class being, therefore, second order transitions instead of infinite order as claimed before.Comment: 11 pages, 5 figure