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 considered to be the quasi-one-dimensional CU2+ (spin-1/2) Heisenberg chain, and the spin-lattice distortion is expressed quasiclassically. We found that the interchain coupling J(perpendicular to) between the chains leads to the occurrence of gapless dimerization (or stepped SP) phase. As the interchain coupling decreases, the difference between the dimerization temperature to and the gap-opening temperature t(G) decreases. If the interchain coupling is small enough, then the difference should be too small to be observed experimentally.