Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

Physical Review B

Initial-value ordinary differential equation solution via variable order Adams method (SIVA/DIVA) package is collection of subroutines for solution of nonstiff ordinary differential equations. There are versions for single-precision and double-precision arithmetic. Requires fewer evaluations of derivatives than other variable-order Adams predictor/ corrector methods. Option for direct integration of second-order equations makes integration of trajectory problems significantly more efficient. Written in FORTRAN 77.

Solving Ordinary Differential Equations

Matter waves inside periodic potentials are well known from solid-state physics, where electrons interacting with a crystal lattice are considered. Atomic Bose-Einstein condensates inside light-induced periodic potentials (optical lattices) share many features with electrons in solids, but also with light waves in nonlinear materials and other nonlinear systems. Generally, atom-atom interactions in Bose-Einstein condensates lead to rich and interesting nonlinear effects. Furthermore, the experimental control over the parameters of the periodic potential and the condensate make it possible to enter regimes inaccessible in other systems. In this review, an introduction to the physics of ultracold bosonic atoms in optical lattices is given and an overview of the theoretical and experimental advances to date.

Dynamics of Bose-Einstein condensates in optical lattices

This paper reviews the recent theoretical and experimental advances in the study of ultra-cold gases made of bosonic particles interacting via the long-range, anisotropic dipole–dipole interaction, in addition to the short-range and isotropic contact interaction usually at work in ultra-cold gases. The specific properties emerging from the dipolar interaction are emphasized, from the mean-field regime valid for dilute Bose–Einstein condensates, to the strongly correlated regimes reached for dipolar bosons in optical lattices. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0034-4885/72/12/126401/pdf

The physics of dipolar bosonic quantum gases

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Emergent Nonlinear Phenomena in Bose-Einstein Condensates

Basic Mean-Field Theory for Bose-Einstein Condensates.- Basic Mean-Field Theory for Bose-Einstein Condensates.- Bright Solitons in Bose-Einstein Condensates.- Bright Solitons in Bose-Einstein Condensates: Theory.- Bright Solitons: Summary of Experimental Techniques.- Dark Solitons in Bose-Einstein Condensates.- Dark Solitons in Bose-Einstein Condensates: Theory.- Dark Solitons in BECs: The First Experiments.- Nonlinear Localization of BECs in Optical Lattices.- Nonlinear Localization of BECs in Optical Lattices.- Multi-Dimensional Solitons in Bose-Einstein Condensates.- Multidimensional Solitons: Theory.- Experiments on Multidimensional Solitons.- Vortices in Bose-Einstein Condensates.- Vortices in Bose-Einstein Condensates: Theory.- Vortices in Bose-Einstein Condensates: Experiments.- Vortex Lattices.- Vortex Lattices in Bose-Einstein Condensates: Theory.- Vortex Lattices in Bose-Einstein Condensates: Experiments.- Optical Lattices.- Optical Lattices: Theory.- Bose-Einstein Condensates in Optical Lattices: Experiments.- Multi-Component Bose-Einstein Condensates.- Multi-Component Bose-Einstein Condensates: Theory.- Multi-Component Condensates: Experiment.- Manipulations of Coherent Matter-Waves.- Manipulations of Coherent Matter-Waves.- Beyond Gross-Pitaevskii Mean Field Theory.- Beyond Gross-Pitaevskii Mean-Field Theory.- Asymptotic Reductions of the Gross-Pitaevskii Equation.- Asymptotic Reductions of the Gross-Pitaevskii Equation.

Emergent nonlinear phenomena in Bose-Einstein condensates : theory and experiment

We report on the generation, subsequent oscillation and interaction of a pair of matter-wave dark solitons. These are created by releasing a Bose-Einstein condensate from a double well potential into a harmonic trap in the crossover regime between one dimension and three dimensions. Multiple oscillations and collisions of the solitons are observed, in quantitative agreement with simulations of the Gross-Pitaevskii equation. An effective particle picture is developed and confirms that the deviation of the observed oscillation frequencies from the asymptotic prediction ${\ensuremath{\nu}}_{z}/\sqrt{2}$, where ${\ensuremath{\nu}}_{z}$ is the longitudinal trapping frequency, results from the dimensionality of the system and the soliton interactions.

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Experimental Observation of Oscillating and Interacting Matter Wave Dark Solitons

An experimentally realizable scheme of periodic sign-changing modulation of the scattering length is proposed for Bose-Einstein condensates similar to dispersion-management schemes in fiber optics. Because of controlling the scattering length via the Feshbach resonance, the scheme is named Feshbach-resonance management. The modulational-instability analysis of the quasiuniform condensate driven by this scheme leads to an analog of the Kronig-Penney model. The ensuing stable localized structures are found. These include breathers, which oscillate between the Thomas-Fermi and Gaussian configuration, or may be similar to the 2-soliton state of the nonlinear Schrodinger equation, and a nearly static state ("odd soliton") with a nested dark soliton. An overall phase diagram for breathers is constructed, and full stability of the odd solitons is numerically established.

Feshbach resonance management for Bose-Einstein condensates.

In this short topical review, we revisit a number of works on the pattern-forming dynamical instabilities of Bose–Einstein condensates in one- and two-dimensional settings. In particular, we illustrate the trapping conditions that allow the reduction of the three-dimensional, mean field description of the condensates (through the Gross–Pitaevskii equation) to such lower dimensional settings, as well as to lattice settings. We then go on to study the modulational instability in one dimension and the snaking/transverse instability in two dimensions as typical examples of long-wavelength perturbations that can destabilize the condensates and lead to the formation of patterns of coherent structures in them. Trains of solitons in one dimension and vortex arrays in two dimensions are prototypical examples of the resulting nonlinear waveforms, upon which we briefly touch at the end of this review.

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Dimitri J. Frantzeskakis

Papers

Emergent Nonlinear Phenomena in Bose-Einstein Condensates

Emergent nonlinear phenomena in Bose-Einstein condensates : theory and experiment

Experimental Observation of Oscillating and Interacting Matter Wave Dark Solitons

Feshbach resonance management for Bose-Einstein condensates.

Pattern forming dynamical instabilities of bose–einstein condensates