Continuous-wave solutions and modulational instability in spinor condensates of positronium

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Vol. 51; no. 4; pp. 45006 - 45018
• Main Authors: Bhat, Ishfaq Ahmad, Mithun, T, Malomed, B A, Porsezian, K
• Format: Journal Article
• Language: English
• Published: IOP Publishing 28.02.2018
• Subjects: continuous-wave solutions; modulational instability; positronium; spinor condensates
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/1361-6455/aaa399

We obtain general continuous-wave (CW) solutions in the model of a spinor positronium condensate in the absence of magnetic field. The CW solutions with both in-phase (n = 0) and out-of-phase (n = 1) spin components exist, with their ranges limited by the total particle density, . In the limit of negligible population exchange between the spin components, the CW solutions are found to be stable or unstable, depending on the particle density of the para-positronium. Ortho-positronium, in the F = 1 spinor state, forms a ferromagnetic condensate with stable in-phase CW solutions only. Subsequent examination of the modulational instability is carried out both in the limit case of identical wavenumbers in the spin components, Δ k k 1 − k − 1 = 0 , and in the more general case of Δ k 0 too. The CW solutions with n = 0 and 1 solutions, which are stable in the case of Δ k = 0 , are unstable for Δ k 0 , for the natural repulsive sign of the nonlinearities. The total particle density, , in the limit of Δ k = 0 is found to have a significant role in the stability of the condensate, which is determined by the sign of the self-interaction nonlinearity.