%0 Journal Article
%T Molecular-field approach to the spin-Peierls transition in CuGeO_3
%A Ralph Werner
%A Claudius Gros
%J Physics
%D 1997
%I arXiv
%R 10.1103/PhysRevB.57.2897
%X We present a theory for the spin-Peierls transition in CuGeO_3. We map the elementary excitations of the dimerized chain (solitons) on an effective Ising model. Inter-chain coupling (or phonons) then introduce a linear binding potential between a pair of soliton and anti-soliton, leading to a finite transition temperature. We evaluate, as a function of temperature, the order parameter, the singlet-triplet gap, the specific heat, and the susceptibility and compare with experimental data on CuGeO_3. We find that CuGeO_3 is close to a first-order phase transition. We point out, that the famous scaling law \sim\delta^{2/3} of the triplet gap is a simple consequence of the linear binding potential between pairs of solitons and anti-solitons in dimerized spin chains.
%U http://arxiv.org/abs/cond-mat/9705099v2