DYNAMICAL STRUCTURE FACTORS OF THE SPIN-1 2 XXZ CHAIN WITH INVERSE-SQUARE EXCHANGE AND ISING ANISOTROPY/

The dynamical properties of the S = 1/2 antiferromagnetic XXZ chain ar e studied by the exact diagonalization and the recursion method of fin ite systems up to 24 sites. Two types of the exchange interaction are considered: one is the nearest-neighbor type, and the other is the inv erse-square one. As the Ising anisotropy becomes larger, there appears a noticeable difference in the transverse component S-xx(q,omega) bet ween the two types of the exchange. For the nearest-neighbor type, the peak frequency of S-xx(q, omega) for each q approaches the center of the continuum spectrum. On the contrary, the peak frequency for the in verse-square type moves to the upper edge of the continuum, and separa tes from the continuum for the anisotropy larger than the threshold va lue. Whether the interaction between domain walls (solitons) is absent or repulsive in the Ising limit leads to this difference in the behav ior of S-xx (q, omega). In the longitudinal component S-zz(q, omega), on the other hand, the feature of the dynamics is scarcely different b etween the two types. The energy gap and the static properties are als o discussed.