Soliton bound states in the Raman spectrum of pure and doped spin-Peierls chains

We investigate the occurrence of singlet bound states in the Raman spectrum of dimerized spin 1/2 chains by exact diagonalization and density matrix renormalization-group techniques. We predict that several bulk δ peaks could be observed in pure systems. Furthermore, we show that additional low-energy lines arise from nonmagnetic impurity doping. These features are interpreted in terms of soliton-antisoliton and soliton-impurity bound states, …