arXiv subjects

H. Susanto

Publications and source records attributed to H. Susanto.

65 records · Page 4Linked to original sources

arXiv2008

Solitons and vortices in honeycomb defocusing photonic lattices

Solitons and necklaces in the first band-gap of a two-dimensional optically induced honeycomb defocusing photonic lattice are theoretically considered. It is shown that dipoles, soliton necklaces, and vortex necklaces exist and may possess regions of stable propagation through a photorefractive crystal. Most of the configurations disappear in bifurcations close to the upper edge of the first band. Solutions associated with such bifurcations are also numerically examined, and it is found that they are often asymmetric and more exotic. The dynamics of the relevant unstable structures are also examined through direct numerical simulations revealing either breathing oscillations or, in some cases, destruction of the original waveform.

nlin.PS↗

arXiv2008

Stability analysis of $π$-kinks in a 0-$π$ Josephson junction

We consider a spatially non-autonomous discrete sine-Gordon equation with constant forcing and its continuum limit(s) to model a 0-$π$ Josephson junction with an applied bias current. The continuum limits correspond to the strong coupling limit of the discrete system. The non-autonomous character is due to the presence of a discontinuity point, namely a jump of $π$ in the sine-Gordon phase. The continuum models admits static solitary waves which are called $π$-kinks and are attached to the discontinuity point. For small forcing, there are three types of $π$-kinks. We show that one of the kinks is stable and the others are unstable. There is a critical value of the forcing beyond all static $π$-kinks fail to exist. Up to this value, the (in)stability of the $π$-kinks can be established analytically in the strong coupling limits. Applying a forcing above the critical value causes the nucleation of $2π$-kinks and -antikinks. Besides a $π$-kink, the unforced system also admits a static $3π$-kink. This state is unstable in the continuum models. By combining analytical and numerical methods in the discrete model, it is shown that the stable $π$-kink remains stable, and that the unstable $π$-kinks cannot be stabilized by decreasing the coupling. The $3π$-kink does become stable in the discrete model when the coupling is sufficiently weak.

nlin.PS↗

arXiv2007

Cerenkov-like radiation in a binary Schr{ö}dinger flow past an obstacle

We consider the dynamics of two coupled miscible Bose-Einstein condensates, when an obstacle is dragged through them. The existence of two different speeds of sound provides the possibility for three dynamical regimes: when both components are subcritical, we do not observe nucleation of coherent structures; when both components are supercritical they both form dark solitons in one dimension (1D) and vortices or rotating vortex dipoles in two dimensions (2D); in the intermediate regime, we observe the nucleation of a structure in the form of a dark-antidark soliton in 1D; subcritical component; the 2D analog of such a structure, a vortex-lump, is also observed.

cond-mat.soft↗

arXiv2006

High-Order-Mode Soliton Structures in Two-Dimensional Lattices with Defocusing Nonlinearity

While fundamental-mode discrete solitons have been demonstrated with both self-focusing and defocusing nonlinearity, high-order-mode localized states in waveguide lattices have been studied thus far only for the self-focusing case. In this paper, the existence and stability regimes of dipole, quadrupole and vortex soliton structures in two-dimensional lattices induced with a defocusing nonlinearity are examined by the theoretical and numerical analysis of a generic envelope nonlinear lattice model. In particular, we find that the stability of such high-order-mode solitons is quite different from that with self-focusing nonlinearity. As a simple example, a dipole (``twisted'') mode soliton which may be stable in the focusing case becomes unstable in the defocusing regime. Our results may be relevant to other two-dimensional defocusing periodic nonlinear systems such as Bose-Einstein condensates with a positive scattering length trapped in optical lattices.

nlin.PS↗

arXiv2006

Dark Solitons in Discrete Lattices: Saturable versus Cubic Nonlinearities

In the present work, we study dark solitons in dynamical lattices with the saturable nonlinearity and compare them with those in lattices with the cubic nonlinearity. This comparison has become especially relevant in light of recent experimental developments in the former context. The stability properties of the fundamental waves, for both on-site and inter-site modes, are examined analytically and corroborated by numerical results. Furthermore, their dynamical evolution when they are found to be unstable is obtained through appropriately crafted numerical experiments.

nlin.PS↗

arXiv2006

Discrete surface solitons in two dimensions

We investigate fundamental localized modes in 2D lattices with an edge (surface). Interaction with the edge expands the stability area for ordinary solitons, and induces a difference between perpendicular and parallel dipoles; on the contrary, lattice vortices cannot exist too close to the border. Furthermore, we show analytically and numerically that the edge stabilizes a novel wave species, which is entirely unstable in the uniform lattice, namely, a "horseshoe" soliton, consisting of 3 sites. Unstable horseshoes transform themselves into a pair of ordinary solitons.

nlin.PS↗

arXiv2006

Mobility of Discrete Solitons in Quadratically Nonlinear Media

We study the mobility of solitons in second-harmonic-generating lattices. Contrary to what is known for their cubic counterparts, discrete quadratic solitons are mobile not only in the one-dimensional (1D) setting, but also in two dimensions (2D). We identify parametric regions where an initial kick applied to a soliton leads to three possible outcomes, namely, staying put, persistent motion, or destruction. For the 2D lattice, it is found that, for the solitary waves, the direction along which they can sustain the largest kick and can attain the largest speed is the diagonal. Basic dynamical properties of the discrete solitons are also discussed in the context of an analytical approximation, in terms of an effective Peierls-Nabarro potential in the lattice setting.

nlin.PS↗

arXiv2006

Stability of Discrete Solitons in the Presence of Parametric Driving

In this brief report, we consider parametrically driven bright solitons in the vicinity of the anti-continuum limit. We illustrate the mechanism through which these solitons become unstable due to the collision of the phase mode with the continuous spectrum, or eigenvelues bifurcating thereof. We show how this mechanism typically leads to complete destruction of the bright solitary wave.

nlin.PS↗

arXiv2004

Controllable plasma energy bands in a 1D crystal of fractional Josephson vortices

We consider a 1D chain of fractional vortices in a long Josephson junction with alternating $\pmκ$ phase discontinuities. Since each vortex has its own eigenfrequency, the inter-vortex coupling results in eigenmode splitting and in the formation of an oscillatory energy band for plasma waves. The band structure can be controlled at the design time by choosing the distance between vortices or \emph{during experiment} by varying the topological charge of vortices or the bias current. Thus one can construct an artificial vortex crystal with controllable energy bands for plasmons.

cond-mat.supr-con↗

arXiv2004

Oscillatory eigenmodes and stability of one and two arbitrary fractional vortices in long Josephson 0-kappa-junctions

We investigate theoretically the eigenmodes and the stability of one and two arbitrary fractional vortices pinned at one and two $κ$-phase discontinuities in a long Josephson junction. In the particular case of a single $κ$-discontinuity, a vortex is spontaneously created and pinned at the boundary between the 0 and $κ$-regions. In this work we show that only two of four possible vortices are stable. A single vortex has an oscillatory eigenmode with a frequency within the plasma gap. We calculate this eigenfrequency as a function of the fractional flux carried by a vortex. For the case of two vortices, pinned at two $κ$-discontinuities situated at some distance $a$ from each other, splitting of the eigenfrequencies occur. We calculate this splitting numerically as a function of $a$ for different possible ground states. We also discuss the presence of a critical distance below which two antiferromagnetically ordered vortices form a strongly coupled ``vortex molecule'' that behaves as a single object and has only one eigenmode.

cond-mat.supr-con↗

arXiv2003

On kink-dynamics of stacked-Josephson junctions

Dynamics of a fluxon in a stack of coupled long Josephson junctions is studied numerically. Based on the numerical simulations, we show that the dependence of the propagation velocity $c$ on the external bias current $γ$ is determined by the ratio of the critical currents of the two junctions $J$.

nlin.PS↗