Spin-Peierls transition in an anisotropic two-dimensional XY model - art. no. 012414

The two-dimensional Jordan-Wigner transformation is used to investigate the zero-temperature spin-Peierls transition for an anisotropic two-dimensiona l XY model in the adiabatic limit. The phase diagram between the dimerized (D) state and uniform (U) state is shown in the parameter space of dimensio nless interchain coupling h (=J(perpendicular to)/J) and spin-lattice coupl ing eta. It is found that the spin-lattice coupling eta must exceed some cr itical value eta (c) in order to reach the D phase for any finite h. The de pendence of eta (c), on It is given by - 1/ln h for h --> \0 and the transi tion between the U and D phases is of first order for at least h>10(-3).