arXiv subjects

Victor M. Perez-Garcia

Publications and source records attributed to Victor M. Perez-Garcia.

At least 55 records · Page 3Linked to original sources

arXiv2003

Stabilized two-dimensional vector solitons

In this letter we introduce the concept of stabilized vector solitons as nonlinear waves constructed by addition of mutually incoherent Townes solitons that are stabilized under the effect of a periodic modulation of the nonlinearity. We analyze the stability of this new kind of structures and describe their behavior and formation in Manakov-like interactions. Potential applications of our results in Bose-Einstein condensation and nonlinear optics are also discussed.

nlin.PS↗

arXiv2003

Scattering of dipole-mode vector solitons: Theory and experiment

We study, both theoretically and experimentally, the scattering properties of optical dipole-mode vector solitons - radially asymmetric composite self-trapped optical beams. First, we analyze the soliton collisions in an isotropic two-component model with a saturable nonlinearity and demonstrate that in many cases the scattering dynamics of the dipole-mode solitons allows us to classify them as ``molecules of light'' - extremely robust spatially localized objects which survive a wide range of interactions and display many properties of composite states with a rotational degree of freedom. Next, we study the composite solitons in an anisotropic nonlinear model that describes photorefractive nonlinearities, and also present a number of experimental verifications of our analysis.

nlin.PS↗

arXiv2003

Stabilization of solitons of the multidimensional nonlinear Schrodinger equation: Matter-wave breathers

We demonstrate that stabilization of solitons of the multidimensional Schrodinger equation with a cubic nonlinearity may be achieved by a suitable periodic control of the nonlinear term. The effect of this control is to stabilize the unstable solitary waves which belong to the frontier between expanding and collapsing solutions and to provide an oscillating solitonic structure, some sort of breather-type solution. We obtain precise conditions on the control parameters to achieve the stabilization and compare our results with accurate numerical simulations of the nonlinear Schrodinger equation. Because of the application of these ideas to matter waves these solutions are some sort of matter breathers.

nlin.PS↗

arXiv2003

Soliton "molecules": robust clusters of light bullets

We show how to generate robust self-sustained clusters of soliton bullets-spatiotemporal (optical or matter-wave) solitons. The clusters carry an orbital angular momentum being supported by competing nonlinearities. The "atoms" forming the "molecule" are fully three-dimensional solitons linked via a staircase-like macroscopic phase. Recent progress in generating atomic-molecular coherent mixing in Bose-Einstein condensates might open potential scenarios for the experimental generation of these soliton molecules with matter-waves.

nlin.PS↗

arXiv2002

Soliton molecules in trapped vector Nonlinear Schrodinger systems

We study a new class of vector solitons in trapped Nonlinear Schrodinger systems modelling the dynamics of coupled light beams in GRIN Kerr media and atomic mixtures in Bose-Einstein condensates. These solitons exist for different spatial dimensions, their existence is studied by means of a systematic mathematical technique and the analysis is made for inhomogeneous media.

nlin.PS↗

arXiv2002

Globally-Linked Vortex Clusters in Trapped Wave Fields

We put forward the existence of a rich variety of fully stationary vortex structures, termed H-clusters, made of an increasing number of vortices nested in paraxial wave fields confined by trapping potentials. However, we show that the constituent vortices are globally linked, rather than products of independent vortices. Also, they always feature a monopolar global wave front and exist in nonlinear systems, such as Bose-Einstein condensates. Clusters with multipolar global wave fronts are non-stationary or at best flipping.

physics.optics↗

arXiv2001

Exact solutions of the two-mode model of multicomponent Bose-Einstein condensates

We find the explicit solution of a two--mode model used to explain vortex dynamics in multicomponent Bose-Einstein condensates. We prove that all the solutions are constants or periodic functions and give explicit formulae for the time evolution of the populations of the two atomic species present in the condensate.

cond-mat.soft↗

arXiv2001

On the applicability of the classical dipole-dipole interaction for polar Bose-Einstein condensates

We argue that the classical form of the dipole-dipole interaction energy cannot be used to model the interaction of the bosons in a dilute Bose-Einstein condensate made of polar atoms. This fact is due to convergence of integrals, if no additional restrictions are introduced. The problem can be regularized, in particular, by introducing a hard sphere model. As an example we propose a regularization consistent with the long range behavior of the effective potential and with the scattering amplitude of the fast particles.

cond-mat.soft↗

arXiv2001

Construction of exact solutions by spatial traslations in inhomogeneous Nonlinear Schrodinger equations. Applications to Bose-Einstein condensation

In this paper we study a general nonlinear Schrödinger equation with a time dependent harmonic potential. Despite the lack of traslational invariance we find a symmetry trasformation which, up from any solution, produces infinitely many others which are centered on classical trajectories. The results presented here imply that, not only the center of mass of the wave-packet satisfies the Ehrenfest theorem and is decoupled from the dynamics of the wave-packet, but also the shape of the solution is independent of the behaviour of the center of the wave. Our findings have implications on the dynamics of Bose-Einstein condensates in magnetic traps

cond-mat.soft↗

arXiv2001

Structural instability of vortices in Bose-Einstein condensates

In this paper we study a gaseous Bose-Einstein condensate (BEC) and show that: (i) A minimum value of the interaction is needed for the existence of stable persistent currents. (ii) Vorticity is not a fundamental invariant of the system, as there exists a conservative mechanism which can destroy a vortex and change its sign. (iii) This mechanism is suppressed by strong interactions.

cond-mat.soft↗

arXiv2000

Vortex nucleation and hysteresis phenomena in rotating Bose-Einstein condensates

We study the generation of vortices in rotating Bose--Einstein condensates, a situation which has been realized in a recent experiment (K. W. Madison, F. Chevy, W. Wohlleben, J. Dalibard, Phys. Rev. Lett. {\bf 84} 806 (2000)). By combining a linear stability analysis with the global optimization of the nonlinear free energy functional, we study the regimes that can be reached in current experiments. We find a hysteresis phenomenon in the vortex nucleation due to the metastabilization of the vortexless condensate. We also prove that for a fast enough rotating trap the ground state of the condensate hosts one or more bent vortex lines.

cond-mat↗

arXiv2000

Optimizing Schroedinger functionals using Sobolev gradients: Applications to Quantum Mechanics and Nonlinear Optics

In this paper we study the application of the Sobolev gradients technique to the problem of minimizing several Schrödinger functionals related to timely and difficult nonlinear problems in Quantum Mechanics and Nonlinear Optics. We show that these gradients act as preconditioners over traditional choices of descent directions in minimization methods and show a computationally inexpensive way to obtain them using a discrete Fourier basis and a Fast Fourier Transform. We show that the Sobolev preconditioning provides a great convergence improvement over traditional techniques for finding solutions with minimal energy as well as stationary states and suggest a generalization of the method using arbitrary linear operators.

math.NA↗

arXiv2000

Solutions of Gross-Pitaevskii equations beyond the hydrodynamic approximation: Application to the vortex problem

We develop the multiscale technique to describe excitations of a Bose-Einstein condensate (BEC) whose characteristic scales are comparable with the healing length, thus going beyond the conventional hydrodynamical approximation. As an application of the theory we derive approximate explicit vortex and other solutions. The dynamical stability of the vortex is discussed on the basis of the mathematical framework developed here, the result being that its stability is granted at least up to times of the order of seconds, which is the condensate lifetime. Our analytical results are confirmed by the numerical simulations.

cond-mat.stat-mech↗

arXiv2000

Stable and unstable vortices in multicomponent Bose-Einstein condensates

We study the stability and dynamics of vortices in two-species condensates as prepared in the recent JILA experiment (M. R. Andrews {\em et al.}, Phys. Rev. Lett. 83 (1999) 2498). We find that of the two available configurations, in which one specie has vorticity $m=1$ and the other one has $m=0$, only one is linearly stable, which agrees with the experimental results. However, it is found that in the unstable case the vortex is not destroyed by the instability, but may be transfered from one specie to the other or display complex spatiotemporal dynamics.

cond-mat.stat-mech↗

arXiv1999

Dipole-Mode Vector Solitons

We find a new type of optical vector soliton that originates from trapping of a dipole mode by a soliton-induced waveguide. These solitons, which appear as a consequence of the vector nature of the two component system, are more stable than the previously found optical vortex-mode solitons and represent a new type of extremely robust nonlinear vector structure.

patt-sol↗

arXiv1999

Two-mode theory of vortex stability in multicomponent Bose-Einstein condensates

We study the stability and dynamics of vortices in two-species condensates using a two mode model. The recent experimental results obtained at JILA (M. R. Matthews, {\em et al.}, Phys. Rev. Lett. 83 (1999) 2498) and theoretical predictions based on the Gross-Pitaevskii equations are verified. We also make an exhaustive analysis of the stability properties of the system when the relative populations of the two species and/or their relative scattering lengths are changed and prove that stabilization of otherwise unstable configurations can be attained by controlling the relative population of both species.

cond-mat↗

arXiv1999

Nonlocal interactions prevent collapse in negative scattering length Bose-Einstein gases

We study the effect of nonlocality on the collapse properties of a self-focusing Nonlinear Schrödinger system related to Bose-Einstein condensation problems. Using a combination of moment techniques, time dependent variational methods and numerical simulations we present evidences in support of the hypothesis that nonlocal attractively interacting condensates cannot collapse when the dominant interaction term is due to finite range interactions. Instead there apppear oscillations of the wave packet with a localized component whose size is of the order of the range of interactions. We discuss the implications of the results to collapse phenomena in negative scattering length Bose-Einstein condensates.

cond-mat↗

arXiv1998

Strong excitations of a Bose--Einstein condensate: Barrier resonances

We study the dynamics of a forced condensed atom cloud and relate the behavior to a classical Mathieu oscillator in a singular potential. It is found that there are wide resonances which can strongly affect the dynamics even when dissipation is present. The behavior is characteristic of condensed clouds of any shape and has experimental relevance.

quant-ph↗