open abstract
The talk aims to give a review of recently obtained results which demonstrate that defocusing cubic media with a spatially inhomogeneous nonlinearity, whose strength increases rapidly enough toward the periphery (faster than r^D in the D-dimensional space, D = 1,2,3, where r is the radial coordinate), give rise to stable solitons (self-trapped localized modes) in all three dimension. These are one-dimensional (1D) fundamental and multihump solitons, 2D dipoles and quadrupoles, including spinning ones, and vortex solitons with an arbitrary topological charge in 2D, and vortex tori (soliton gyroscopes and Hopfions, i.e., intrinsically twisted tori with two independent topological numbers) in 3D. Solitons maintain their coherence in the state of motion, oscillating in the effective nonlinear trapping potential as robust objects. The 3D vortex tori exhibit stable precession and rotation, induced by the application of external torque. In addition to numerically found soliton families, particular solutions can be obtained in an exact analytical form, and accurate analytical approximations are available for the entire families, based on variational and Thomas-Fermi methods. Essentially the same mechanism for the self-trapping of bright solitons under the action of the spatially growing repulsive nonlinearity works in nonlocal media, and in discrete systems too, including the corresponding version of the quantum Bose-Hubbard model. Spontaneous symmetry breaking of the solitons in the 1D and 2D local-nonlinearity modulation profiles with the double-wall structure has been found too. Furthermore, numerical and analytical results demonstrate the existence of stable solitons in a PT-symmetric extension of the 1D model, and of stable dissipative solitons in media combining a uniform linear gain and nonlinear loss whose local strength grows toward the periphery faster than r^D. Such 1D and 2D settings can be implemented both in nonlinear optics and Bose-Einstein condensates (BEC), while the 3D setting may be created in BEC.
[1] R. Driben, Y. V. Kartashov, B. A. Malomed, T. Meier, and L. Torner, "Soliton gyroscopes in media with spatially growing repulsive nonlinearity", Phys. Rev. Lett. 112, 020404 (2014)
[2] R. Driben, Y. Kartashov, B. A. Malomed, T. Meier, and L. Torner, "Three-dimensional hybrid vortex solitons", New J. Phys. 16, 063035 (2014)
[3] Y. V. Kartashov, B. A. Malomed, Y. Shnir, and L. Torner, "Twisted toroidal vortex-solitons in inhomogeneous media with repulsive nonlinearity", Phys. Rev. Lett. 113, 264101 (2014).
[4] R. Driben, T. Meier, and B. A. Malomed, "Creation of vortices by torque in multidimensional media with inhomogeneous defocusing nonlinearity", Sci. Rep. 5, 9420 (2015)
[5] R. Driben, N. Dror, B. Malomed, and T. Meier, "Multipoles and vortex multiplets in multidimensional media with inhomogeneous defocusing nonlinearity", New J. Phys. 17, 083043 (2015).