Unusual quantum phase in exactly solvable doubly decorated Ising-Heisenberg models

Ground-state properties of the spin-1/2 and spin-1 Ising-Heisenberg model on doubly decorated planar lattices, are investigated in detail. On the basis of the mapping transformation method, we prove an existence of unusual quantum phases which occur due to the competition between Ising-type and XXZ anizotropic Heisenberg-type interactions. Effect of the crystal field on the ground-state phase boundaries has been also examined in detail.