Solitons in the spin-Peierls compound CuGeO 3

We calculate the excitation gap, the soliton energy, and the soliton density at finite temperature, of the spin-1/2 one dimensional antiferromagnet coupled to phonons, using a self-consistent harmonic approximation, and the thermal-Green function technique. The spin degrees of freedom are represented by the phase Hamiltonian with the help of the boson representation of the spinless fermions. We estimate the critical field Hc above which begins the incommensurate phase. We also present a theoretical calculation for the specific heat in this phase. We use CuGeO3 as an example of a compound where our theory could be applied.