Magnetic excitations in quasi-two-dimensional spin-Peierls systems

A study is presented of a two-dimensional frustrated and dimerized quantum spin system which models the effect of interchain coupling in a spin-Peierls compound. Employing a bond-boson method to account for quantum disorder in the ground state the elementary excitations are evaluated in terms of gapful triplet modes. Results for the ground-state energy and the spin gap are discussed. The tripler dispersion is found to be in excellent agreement with inelastic neutron scattering data in the dimerized phase of the spin-Peierls compound CuGeO3. Moreover, consistent with these neutron scattering experiments, the low-temperature dynamic structure factor exhibits a high-energy continuum split off from the elementary triplet mode.