Magnetization plateaus and phase diagram in polymerized S=1/2 XXZ chains -art. no. 134427

The magnetization plateaus of polymerized S = 1/2 XXZ chains are studied fo r general values of p. Two plateau-non-plateau critical lines and one plate au-plateau critical line are found for each value of p. The universality cl ass of the plateau-non-plateau transition belongs to the Brezinskii-Kosterl itz-Thouless type and that of the plateau-plateau transition, to the Gaussi an type. The critical points are determined by level spectroscopic analysis of the numerical diagonalization results for 4 less than or equal top less than or equal to8. The multicritical points are calculated using the integ ral equations based on the Bethe ansatz solution of the XXZ model. The beha vior of multicritical points are analyzed in detail for large p. It is foun d that the plateau region is enhanced with the increase in periodicity p al though the nonplateau region persists as far as p is finite.