The spin-Peierls phase transition in the quasi-one-dimensional spin-1/2 Heisenberg model

The spin-Peierls (SP) phase transition of the inorganic compound CuGeO3 is theoretically studied on the basis of Heisenberg model using Jordan-Wigner transformation (JWT) by mean-field approach. The magnetic interaction is co nsidered to be the quasi-one-dimensional CU2+ (spin-1/2) Heisenberg chain, and the spin-lattice distortion is expressed quasiclassically. We found tha t the interchain coupling J(perpendicular to) between the chains leads to t he occurrence of gapless dimerization (or stepped SP) phase. As the interch ain coupling decreases, the difference between the dimerization temperature to and the gap-opening temperature t(G) decreases. If the interchain coupl ing is small enough, then the difference should be too small to be observed experimentally.