Unbreakable PT symmetry of solitons supported by inhomogeneous defocusing nonlinearity

Yaroslav V. Kartashov*, Boris A. Malomed, Lluis Torner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We consider bright solitons supported by a symmetric inhomogeneous defocusing nonlinearity growing rapidly enough toward the periphery of the medium, combined with an antisymmetric gain-loss profile. Despite the absence of any symmetric modulation of the linear refractive index, which is usually required to establish a parity-time (PT ) symmetry in the form of a purely real spectrum of modes, we show that the PT symmetry is never broken in the present system, and that the system always supports stable bright solitons, i.e., fundamental and multipole ones. This fact is connected to the nonlinearizability of the underlying evolution equation. The increase of the gain - loss strength results, in lieu of the PT symmetry breaking, in merger of pairs of different soliton branches, such as fundamental and dipole, or tripole and quadrupole ones. The fundamental and dipole solitons remain stable at arbitrarily large values of the gain-loss coefficient.

Original languageEnglish
Pages (from-to)5641-5644
Number of pages4
JournalOptics Letters
Issue number19
StatePublished - 1 Oct 2014


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