Phase diagrams, quantum correlations and critical phenomena of antiferromagnetic Heisenberg model on diamond-type hierarchical lattices

The spin-1/2 antiferromagnetic Heisenberg systems are studied on three typical diamond-type hierarchical lattices (systems A, B and C) with fractal dimensions 1.63, 2 and 2.58, respectively, and the phase diagrams, critical phenomena and quantum correlations are calculated by a combination of the equivalent transformation and real-space renormalization group methods. We find that there exist a reentrant behavior for system A and a finite temperature transition in the isotropic Heisenberg limit for system C (not for system B). Unlike the ferromagnetic case, the Neel temperatures of antiferromagnetic systems A and B are inversely proportional to ln(Delta_c-Delta) (when Delta->Delta_c) and ln Delta (when Delta->0), respectively. And we also find that there is a turning point of quantum correlation in the isotropic Heisenberg limit Delta=0 where there is a peak of the contour and no matter how large the size of system is, quantum correlation will change to zero in the Ising limit for the three systems. The quantum correlation decreases with the increase of lattice size L and it is almost zero when L>=30 for system A, and for systems B and C, they still exist when L is larger than that of system A. Moreover, as an example, we discuss the error of result in system A, which is induced by the noncommutativity.
Comment: 28 pages, 13 figures