Nonautonomous deformed solitons in a Bose-Einstein condensate

We study exact single-soliton solutions of an attractive Bose-Einstein condensate governed by a one-dimensional nonautonomous Gross-Pitaevskii system. For several different forms of time-dependent atom-atom interaction and external parabolic potential which satisfy the exact integrability scenario, we construct a set of new analytical nonautonomous deformed-soliton solutions, including the macroscopic wave function and the position of soliton＇s center of mass. The soliton characteristics are modulated by the external field parameters and deformation factors related to the number of the condensed atoms and the initial conditions. The results suggest a simple and effective method for experimentally generating matter-wave deformed solitons and manipulating their motions.     

Dark solitons in a two-component Bose-Einstein condensate

The creation and interaction of dark solitons in a two-component Bose-Einstein condensate is investigated. For a miscible case, the interaction of dark solitons in different components is studied. Various possible scenarios are presented, including the formation of a soliton-soliton bound pair. We also analyze the soliton propagation in the presence of domains, and show that a dark soliton can be transferred from one component to the other at the domain wall when it exceeds a critical velocity. For lower velocities multiple reflections within the domain are observed, where the soliton is evaporated and accelerated after each reflection until it finally escapes from the domain.     

Dissipative dynamics of a harmonically confined Bose-Einstein condensate

We study the dissipation of the center of mass oscillation of a harmonically confined condensate in the presence of a disorder potential. An extension of the harmonic potential theorem allows one to formulate the dynamics from the point of view of an oscillating disorder potential. This formulation leads to a rigorous result for the damping rate in the limit of weak disorder.     

Internal modes of solitons in a Bose-Einstein condensate

A modified Gross-Pitaevskii equation for a Bose-Einstein condensate with nonlocal interaction between atoms is used to analyze and calculate the characteristics of internal modes of bright solitons (eigen-modes of small perturbations of the condensate). The spectra of even and odd internal modes are found for one-and two-dimensional solitons, and the rate constant characterizing nonlinear internal-mode damping is determined. The possibility of experimental verification of the results is discussed.     

玻色-爱因斯坦凝聚体中的双孤子相互作用操控

考虑周期性驱动线性势, 利用Darboux变换法解析地研究了玻色-爱因斯坦凝聚体(BEC)中的双孤子相互作用, 得到了S-波散射长度的临界值. 结果表明: 当S-波散射长度高于临界值时, BEC中的两个亮孤子相互吸引并融合; 而当S-波散射长度低于临界值时, 两个亮孤子保持局域稳定. 此外, 在外部势阱的驱动下, 两个稳定的亮孤子产生周期性振荡行为.     

Precisely controllable bright nonautonomous solitons in Bose-Einstein condensate

We study on bright nonautonomous solitons of Bose-Einstein condensate analytically in a time-dependent harmonic trap with an arbitrary time-dependent linear potential and complex potential. The explicit ways to control dynamics of soliton are presented through observing the evolution of its width, peak, and the motion of its center analytically. Furthermore, we present two-solitons solution in generalized form to observe the collision of solitons conveniently.     

Topological solitons and Bloch oscillations in Bose-Einstein condensate

We studied the evolution of topological solitons in the space of its width d and the conjugated momenta l during Bloch oscillations. The unstable solitons are confined in a well with its boundary as four branches of a hyperbola, the stable solitons sit at the four branches of the hyperbola (d · l = 28) which is in agreement with the generalized Heisenberg uncertainty principal Δd · Δl ? Const. The generation, annihilation, and bifurcation of solitons is going on in the well. In studying the behavior of the nonlinear interaction parameter for the stable solitons, it is found that bright solitons and dark solitons alternatively come into action during the breakdown and revival of Bloch oscillations.     

Moving bright solitons in a pseudo-spin polarization Bose-Einstein condensate

We study the moving bright solitons in the weak attractive Bose–Einstein condensate with a spin–orbit interaction. By solving the coupled nonlinear Schr ?dinger equation with the variational method and the imaginary time evolution method,two kinds of solitons(plane wave soliton and stripe solitons) are found in different parameter regions. It is shown that the soliton speed dominates its structure. The detuning between the Raman beam and energy states of the atoms decides the spin polarization strength of the system. The soliton dynamics is also studied for various moving speed and we find that the shape of individual components can be kept when the speed of soliton is low.     

Oblique dark solitons in supersonic flow of a Bose-Einstein condensate

In the framework of the Gross-Pitaevskii mean field approach, it is shown that the supersonic flow of a Bose-Einstein condensate can support a new type of pattern--an oblique dark soliton. The corresponding exact solution of the Gross-Pitaevskii equation is obtained. It is demonstrated by numerical simulations that oblique solitons can be generated by an obstacle inserted into the flow.     

Dynamics of solitons in Bose-Einstein condensate with time-dependent atomic scattering length

The evolution of solitons in Bose--Einstein condensates (BECs) with time-dependent atomic scattering length in an expulsive parabolic potential is studied. Based on the extended hyperbolic function method, we successfully obtain the bright and dark soliton solutions. In addition, some new soliton solutions in this model are found. The results in this paper include some in the literature ({\em Phys. Rev. Lett.} {\bf 94} (2005) 050402 and {\em Chin. Phys. Lett.} {\bf 22} (2005) 1855).     

Watching dark solitons decay into vortex rings in a Bose-Einstein condensate

We have created spatial dark solitons in two-component Bose-Einstein condensates in which the soliton exists in one of the condensate components and the soliton nodal plane is filled with the second component. The filled solitons are stable for hundreds of milliseconds. The filling can be selectively removed, making the soliton more susceptible to dynamical instabilities. For a condensate in a spherically symmetric potential, these instabilities cause the dark soliton to decay into stable vortex rings. We have imaged the resulting vortex rings.     

Response of a Bose-Einstein condensate of dipole excitons to static and dynamic perturbations

Studies of the interaction of a Bose-Einstein condensate of two-dimensional spatially indirect excitons with the static fields of impurities, surface acoustic waves, and elementary excitations of a degenerate electron gas have been reviewed. The effects of screening of charged impurities and absorption of a Bleustein-Gulyaev surface acoustic wave by an exciton condensate have been considered. Friedel oscillations of the exciton density in a hybrid electron-exciton system, which consists of spatially separated layers of condensed exciton gas and degenerate electron gas, have been studied. The lifetimes of quasiparticle excitations (electrons, plasmons, and bogolons) in the hybrid system have been calculated. The contributions to the effects under study from condensate and above-condensate particles have been determined. The properties of an excitonic insulator have been analyzed within the Bardeen-Cooper-Schrieffer model with a built-in dissipation-free current.     

Incoherent matter-wave solitons and pairing instability in an attractively interacting Bose-Einstein condensate

The dynamics of matter-wave solitons in Bose-Einstein condensates (BEC) is considerably affected by the presence of a thermal cloud and the dynamical depletion of the condensate. Our numerical results, based on the time-dependent Hartree-Fock-Bogoliubov theory, demonstrate the collapse of the attractively interacting BEC via collisional emission of atom pairs into the thermal cloud, which splits the (quasi-one-dimensional) BEC soliton into two partially coherent solitonic structures of opposite momenta. These incoherent matter waves are analogous to optical random-phase solitons.     

Effects of parameters on the stationary state and self-trapping of three coupled Bose-Einstein condensate solitons

The stability of three coupled Bose-Einstein condensate (BEC) solitons is investigated by the variational approach in two conventional time-independent trapping potentials.     

Stabilization of solitons generated by a supersonic flow of Bose-Einstein condensate past an obstacle

The stability of dark solitons generated by supersonic flow of a Bose-Einstein condensate past an obstacle is investigated. It is shown that in the reference frame attached to the obstacle a transition occurs at some critical value of the flow velocity from absolute instability of dark solitons to their convective instability. This leads to the decay of disturbances of solitons at a fixed distance from the obstacle and the formation of effectively stable dark solitons. This phenomenon explains the surprising stability of the flow picture that has been observed in numerical simulations.     

Effects of external magnetic trap on two dark solitons of a two-component Bose-Einstein condensate

Two dark solitons are considered in a two-component Bose-Einstein condensate with an external magnetic trap, and effects of the trap potential on their dynamics are investigated by the numerical simulation. The results show that the dark solitons attract, collide and repel periodically in two components as time changes, the time period depends strictly on the initial condition and the potential, and there are obvious self-trapping effects on the two dark solitons.     

Dissipative molecular solitons

Theoretical analysis and numerical simulations of resonance interaction of laser radiation with a linear molecular chain have been performed. The regimes of switching waves and dissipative solitons, whose sizes for J-aggregates can reach nanometer range, have been demonstrated.     

Effects of three-body atomic interaction and optical lattice on solitons in quasi-one-dimensional Bose-Einstein condensate

We make use of a coordinate-free approach to implement Vakhitov-Kolokolov criterion for stability analysis in order to study the effects of three-body atomic recombination and lattice potential on the matter-wave bright solitons formed in Bose-Einstein condensates. We analytically demonstrate that (i) the critical number of atoms in a stable BEC soliton is just half the number of atoms in a marginally stable Townes-like soliton and (ii) an additive optical lattice potential further reduces this number by a factor of √1 − bg ₃ with g ₃ the coupling constant of the lattice potential and b = 0.7301.      

Magnetized vector solitons in a spin-orbit coupled spin-1 Bose-Einstein condensate with Zeeman coupling

The property of matter-wave vector solitons in a spin-1 Bose-Einstein condensate with spin-orbit and Zeeman couplings is investigated by multiscale perturbation method. The excitation spectrum and the corresponding state vectors of the system are obtained analytically, and they can be adjusted by the parameters of the system. The bright and dark vector solitons are formulated by reducing the three-component coupled Gross-Pitaeviskii equations to a standard nonlinear Schrödinger equation, which has the solutions of the bright and dark solitons with positive or negative mass depending on the product of the effective dispersive and nonlinear coefficients. The moving vector solitons are demonstrated by adjusting specific momentum near the energy minimum. Finally, the magnetized features of the vector solitons are discussed by the spin polarization of the system.