Multi-pole solitons in nonlocal nonlinear media with fourth-order diffraction

This paper studies the existence and stability of solitons in nonlocal nonlinear media (NNM) with the fourth-order diffraction, and reveals that the coupling constant of the fourth-order diffraction plays a significant role in destabilizing the propagations of the solitons. Such as in the local nonlinear media, the fundamental solitons are stable in the low coupling constant domains, but cannot exist in the high coupling constant regions. For the exponential-decay response, the maximal number of peaks in stable multipole solitons are dipole and quadrupole in NNM with and without the fourth-order diffraction, respectively. For the Gaussian-shaped response, the solitons exhibit novel structures, where the inner humps of the tripole and quadrupole solitons decrease as the β decreases. The evolutions of solitons with perturbation are also investigated to confirm their stability.