Intermediate magnetization plateaus in the spin-1/2 Ising-Heisenberg and Heisenberg models on two-dimensional triangulated lattices

摘要

The ground state and zero-temperature magnetization process of the spin-1/2Ising-Heisenberg model on two-dimensional triangles-in-triangles lattices isexactly calculated using eigenstates of the smallest commuting spin clusters.Our ground-state analysis of the investigated classical--quantum spin modelreveals three unconventional dimerized or trimerized quantum ground statesbesides two classical ground states. It is demonstrated that the spinfrustration is responsible for a variety of magnetization scenarios with up tothree or four intermediate magnetization plateaus of either quantum orclassical nature. The exact analytical results for the Ising-Heisenberg modelare confronted with the corresponding results for the purely quantum Heisenbergmodel, which were obtained by numerical exact diagonalizations based on theLanczos algorithm for finite-size spin clusters of 24 and 21 sites,respectively. It is shown that the zero-temperature magnetization process ofboth models is quite reminiscent and hence, one may obtain some insight intothe ground states of the quantum Heisenberg model from the rigorous results forthe Ising-Heisenberg model even though exact ground states for theIsing-Heisenberg model do not represent true ground states for the pure quantumHeisenberg model.