Physical Review E

Modulational instability of a modified Gross-Pitaevskii equation with higher-order nonlinearity

Xiu-Ying Qi, Ju-Kui Xue

Published Jul 2, 2012• 27 citations

Abstract

We consider the modulational instability (MI) of Bose-Einstein condensate (BEC) described by a modified Gross-Pitaevskii (GP) equation with higher-order nonlinearity both analytically and numerically. A new explicit time-dependent criterion for exciting the MI is obtained. It is shown that the higher-order term can either suppress or enhance the MI, which is interesting for control of the system instability. Importantly, we predict that with the help of the higher-order nonlinearity, the MI can also take place in a BEC with repulsively contact interactions. The analytical results are confirmed by direct numerical simulations.

DOI: 10.1103/physreve.86.017601

Related papers

Modulational instability for a cubic-quintic model of coupled Gross–Pitaevskii equations with residual nonlinearities

Maïk Delon Mboumba, Marius Romuald Kamsap, A. B. Moubissi +2 more

Abstract We demonstrate the existence of modulational instability (MI) in both trapped miscible and immiscible two component Bose–Einstein condensates. The study is addressed theoretically and numerically in the framework of one-dimensional coupled Gross–Pitaevskii equations incorporating intra- and interspecies cubic-quintic nonlinearities with higher-order ones. Using the time-dependent variational approach, we derive the new Euler-Langrange equations for the time evolution of the phase and amplitude of the modulational perturbation as well as the effective potential and the instability criteria of the system. We examine the effects of higher order nonlinearities on the instability dynamics of the condensates. We show that the modulational properties of the chosen wave numbers are significantly modified. Direct numerical simulations run by the split step Fourier method confirm the analytical predictions.

Physica ScriptaNov 6, 20240 citations

MODULATIONAL INSTABILITY OF A BOSE–EINSTEIN CONDENSATE BEYOND THE FERMI PSEUDOPOTENTIAL WITH A TIME-DEPENDENT COMPLEX POTENTIAL

D. Belobo Belobo, G. H. Ben-Bolie, Thierry Blanchard Ekogo +2 more

The modulational instability (MI) of Bose–Einstein condensates based on a modified Gross–Pitaevskii equation (GPE) which takes into account quantum fluctuations and a shape-dependent term, trapped in an external time-dependent complex potential is investigated. The external potential consists of an expulsive parabolic background with a complex potential and a gravitational field. The theoretical analysis uses a modified lens-type transformation which converts the modified GPE into a modified form without an explicit spatial dependence. A MI criterion and a growth rate are explicitly derived, both taking into account quantum fluctuations and the parameter related to the feeding or loss of atoms in the condensate which significantly affect the gain of instability of the condensate. Direct numerical simulations of the modified GPE show convincing agreements with analytical predictions. In addition, our numerical results also reveal that the gravitational field has three effects on the MI: (i) the deviation backward or forward of solitons trains, (ii) the enhancement of the appearance of the MI and (iii) the reduction of the lifetime of pulses. Moreover, numerical simulations proved that it is possible to control the propagation of the generated solitons trains by a proper choice of parameters characterizing both the loss or feeding of atoms and the gravitational field, respectively.

International Journal of Modern Physics BSep 30, 201212 citations

Impact of higher-order nonlinearity on modulational instability in two-component Bose-Einstein condensates

Tamilthiruvalluvar Ramakrishnan, Étienne Wamba, Subramaniyan Sabari +1 more

We investigate the effect of higher-order interactions induced by shape-dependent confinement in the modulational instability (MI) of a binary mixture of Bose-Einstein condensates. For this, we present and compute both analytically and numerically a system of coupled Gross-Pitaevskii equations with residual nonlinearity that rule the dynamics of the mixture. Using the linear stability approach, we obtain the instability criteria of the mixture and find that the MI can be excited in miscible condensates and altered in immiscible condensates due to the effect of residual nonlinearity. Direct numerical calculations are performed to support the analytical predictions, and a good agreement is found. The space-time evolution of the condensate density is displayed in both cases when the mixture is miscible and immiscible, showing the generation of bright solitons for modes predicted to be unstable.

Physical review. EMar 5, 201927 citations

Dynamical instability of a Bose-Einstein condensate with higher-order interactions in an optical potential through a variational approach

Étienne Wamba, Subramaniyan Sabari, Kuppuswamy Porsezian +2 more

We investigate the dynamical instability of Bose-Einstein condensates (BECs) with higher-order interactions immersed in an optical lattice with weak driving harmonic potential. For this, we compute both analytically and numerically a modified Gross-Pitaevskii equation with higher-order nonlinearity and external potentials generated by magnetic and optical fields. Using the time-dependent variational approach, we derive the ordinary differential equations for the time evolution of the amplitude and phase of modulational perturbation. Through an effective potential, we obtain the modulational instability condition of BECs and discuss the effect of the higher-order interaction in the dynamics of the condensates in presence of optical potential. We perform direct numerical simulations to support our analytical results, and good agreement is found.

arXiv:1404.5411Physical Review EMay 29, 201425 citations

THREE-BODY INTERACTIONS BEYOND THE GROSS–PITAEVSKII EQUATION AND MODULATIONAL INSTABILITY OF BOSE–EINSTEIN CONDENSATES

D. Belobo Belobo, G. H. Ben-Bolie, Timoléon Crépin Kofané

Beyond the mean-field theory, a new model of the Gross–Pitaevskii equation (GPE) that describes the dynamics of Bose–Einstein condensates (BECs) is derived using an appropriate phase-imprint on the old wavefunction. This modified version of the GPE in addition to the two-body interactions term, also takes into account effects of the three-body interactions. The three-body interactions consist of a quintic term and the delayed nonlinear response of the condensate system term. Then, the modulational instability (MI) of the new GPE confined in an attractive harmonic potential is investigated. The analytical study shows that the three-body interactions destabilize more the condensate system while the external potential alleviates the instability. Numerical results confirm the theoretical predictions. Further numerical investigations of the behavior of solitons reveal that the three-body interactions enhance the appearance of solitons, increase the number of solitons generated and deeply change the lifetime of solitons. Moreover, the external potential delays the appearance of solitons. Besides, a new initial condition is introduced which enables to increase the number of solitons created and deeply affects the trail of chains of solitons generated. Moreover, the MI of a condensate without the external potential, and in a repulsive potential is also investigated.

International Journal of Modern Physics BNov 8, 20124 citations

Effects of residual nonlinearities on the modulational instability of three-component Bose–Einstein condensates

P. Mohanraj, R. Sivakumar

Abstract We study the modulation instability in a three-component Bose–Einstein condensate and the impact of higher-order interactions brought on by shape-dependent confinement. Using the modified Gross–Pitaevskii equation that accounts for the higher-order residual nonlinearity and the linear stability method, we analyze the dispersion relations and the gain spectrum for instability. In particular, we investigate the role of higher-order interactions over the MI in miscible and immiscible condensates. The observed MI spectrum shows a new regime for soliton generation in a ternary mixture of Bose–Einstein condensates. Our results show that the residual nonlinearity can effectively control the MI gain profile in both miscible and immiscible condensates. This allows one manipulate the MI in a ternary mixture of Bose–Einstein condensates to control the dynamics.

Physica ScriptaJul 18, 20232 citations