Stability and symmetry breaking of soliton bound states

With the variational method we analytically study rotating vector soliton bound states in Kerr media. A standard linear stability analysis reveals that, in the presence of nonlinear birefringence, these soliton bound states exhibit a symmetry-breaking instability. In the absence of nonlinear birefringence, that is, in the Manakov system, the bound states are shown to be neutrally stable and not robust against soliton collisions. We show that these stability properties are not influenced by saturation of the nonlinearity, a result that is relevant to recent experimental observations of soliton bound states in photorefractive media.