Theory for low-lying excitations in the spin-Peierls system CuGeO3 -: art. no. 054421

Using the bosonization technique and self-consistent quantum theory, we study two branches of low-lying excitation in the spin-Peierls system CuGeO3 with frustration. The energy gaps of triplet one-magnon excited state and singlet two-magnon bound state are calculated for a set of parameters appropriate to the compound CuGeO3. The calculated results are consistent with experimental data of CuGeO3. It is found that the energy gaps of the one- and two-magnon states increase with increasing either frustration or dimerization parameter. As the dimerization is increased, the binding energy of the singlet two-magnon bound state increases for smaller frustration, whereas it decreases for larger frustration. The power-law relation between the binding energy and the dimerization exists for small dimerization and at criticality alpha = alpha(c) = 0.2411.