Search Results for « Soliton states »

A detailed study of the stability of the soliton states for a nonlinear fiber coupler is presented. It is shown that the stability of the symmetric soliton states is delimited by the point of bifurcation: symmetric states are stable starting from zero energy up to the point of bifurcation, and unstable beyond the point of bifurcation. Asymmetric A-type states are stable at points with positive slope in the energy dispersion curve, and unstable otherwise. B-type asymmetric states are always unstable. Antisymmetric soliton states have regions of unstable as well as stable behavior. Moreover, the perturbation growth rate for the antisymmetric states can be complex in a certain range of spatial frequencies. A close analogy between the stability results for the soliton states in a nonlinear coupler and those for guided waves in planar nonlinear structures is established.

Dark soliton states of Bose-Einstein condensates in harmonic traps are studied both analytically and computationally by the direct solution of the Gross-Pitaevskii equation in three dimensions. The ground and self-consistent excited states are found numerically by relaxation in imaginary time. The energy of a stationary soliton in a harmonic trap is shown to be independent of density and geometry for large numbers of atoms. Large-amplitude field modulation at a frequency resonant with the energy of a dark soliton is found to give rise to a state with multiple vortices. The Bogoliubov excitation spectrum of the soliton state contains complex frequencies, which disappear for sufficiently small numbers of atoms or large transverse confinement. The relationship between these complex modes and the snake instability is investigated numerically by propagation in real time.

We consider stationary soliton states in a birefringent optical fiber with two components locked in phase. Two values of the phase difference between the two components of the soliton states are studied: 0 and π/2. These cases allow us to find composite soliton states in a simple way. The bifurcation diagrams for the coupled soliton states in these two cases are constructed. The stability of these soliton states is examined also.

Several two-dimensional quantum field theory models have more than one vacuum state. Familiar examples are the Sine-Gordon and the [Formula: see text]-model. It is known that in these models there are also states, called soliton or kink states, which interpolate different vacua. We investigate the following question: Which are the properties a pair of vacuum states must have, such that an interpolating kink state can be constructed? We discuss the problem in the framework of algebraic quantum field theory which includes, for example, the P(ϕ)2-models. We identify a large class of vacuum states, including the vacua of the P(ϕ)2-models, for which there is a natural way to construct an interpolating kink state.

Dissipative Kerr solitons have recently been generated in optical microresonators, enabling ultrashort optical pulses at microwave repetition rates, that constitute coherent and numerically predictable Kerr frequency combs. However, the seeding and excitation of the temporal solitons is associated with changes in the intracavity power that can lead to large thermal resonance shifts and render the soliton states in most commonly used resonator platforms short lived. Here we describe a "power kicking" method to overcome this instability by modulating the power of the pump laser. With this method also initially very short-lived (of the order of 100 ns) soliton states can be brought into a steady state in contrast to techniques reported earlier which relied on an adjustment of the laser scan speed only. Once the soliton state is in a steady state it can persist for hours and is thermally self-locked.

In the framework of the Ginzburg-Landau approach, we present a self-consistent theory of specific soliton states in mesoscopic (thin-walled) two-band-superconducting cylinders in external parallel magnetic fields. Such states arise in the presence of “Josephson-type” interband coupling, when phase winding numbers are different for each component of the superconducting order parameter. We evaluate the Gibbs free energy of the system up to second-order terms in a certain dimensionless parameter ɛ≈Lm/Lk≪1, where Lm and Lk are the magnet and kinetic inductance, respectively. We derive the complete set of exact soliton solutions. These solutions are thoroughly analyzed from the viewpoint of both local and global (thermodynamic) stability. In particular, we show that rotational-symmetry-breaking caused by the formation of solitons gives rise to a zero-frequency rotational mode. Although soliton states prove to be thermodynamically metastable, the minimal energy gap between the lowest-lying single-soliton states and thermodynamically stable zero-soliton states can be much smaller than the magnetic Gibbs free energy of the latter states, provided that intraband “penetration depths” differ substantially and interband coupling is weak. The results of our investigation may apply to a wide class of mesoscopic doubly-connected structures exhibiting two-band superconductivity.

The focusing nonlinear Schrodinger equation possesses special non-dispersive solitary type solutions, solitons. Under certain spectral assumptions we show existence and asymptotic stability of solutions with the asymptoic profile (as time goes to infinity) of a linear combination of N non-colliding solitons.

We present a numerically exact study of self-trapped (also referred to as soliton) states of electrons that form in materials with strong quadratic coupling to the phonon coordinates. Previous studies failed to observe predictions based on the variational approach in continuum space because soliton states form only when system parameters are taken to the extreme limit. At the variational level, we establish that finite-radius solitons emerge through the weak first-order transition as the coupling strength is increased, and subsequently collapse to the single-site state through a strong first-order transition. Both transitions transform into smooth crossovers between the light and heavy polaron states in the full quantum treatment. The most surprising effect not observed in other polaron models is the nonmonotonic dependence of the soliton effective mass and the residue at strong coupling.

The quantum nonlinear schrödinger equation (QNSE) is exactly solved by Beth's ansatz method and we give a reasonable definition of the quantum soliton states. From the definition we construct the soliton states of the QNSE from its bound-state solutions. The dispersion effect of the quantum soliton is also exactly analysed.

Dilute-gas Bose-Einstein condensates are an exceptionally versatile test bed for the investigation of novel solitonic structures. While matter-wave solitons in one- and two-component systems have been the focus of intense research efforts, an extension to three components has never been attempted in experiments. Here, we experimentally demonstrate the existence of robust dark-bright-bright (DBB) and dark-dark-bright solitons in a multicomponent F=1 condensate. We observe lifetimes on the order of hundreds of milliseconds for these structures. Our theoretical analysis, based on a multiscale expansion method, shows that small-amplitude solitons of these types obey universal long-short wave resonant interaction models, namely, Yajima-Oikawa systems. Our experimental and analytical findings are corroborated by direct numerical simulations highlighting the persistence of, e.g., the DBB soliton states, as well as their robust oscillations in the trap.