592 research outputs found
Dynamics and Manipulation of Matter-Wave Solitons in Optical Superlattices
We analyze the existence and stability of bright, dark, and gap matter-wave
solitons in optical superlattices. Then, using these properties, we show that
(time-dependent) ``dynamical superlattices'' can be used to controllably place,
guide, and manipulate these solitons. In particular, we use numerical
experiments to displace solitons by turning on a secondary lattice structure,
transfer solitons from one location to another by shifting one superlattice
substructure relative to the other, and implement solitonic ``path-following'',
in which a matter wave follows the time-dependent lattice substructure into
oscillatory motion.Comment: 6 pages, revtex, 6 figures, to appear in Physics Letters A; minor
modifications from last versio
Nonlinear localized modes in two-dimensional electrical lattices
We report the observation of spontaneous localization of energy in two
spatial dimensions in the context of nonlinear electrical lattices. Both
stationary and traveling self-localized modes were generated experimentally and
theoretically in a family of two-dimensional square, as well as hon- eycomb
lattices composed of 6x6 elements. Specifically, we find regions in driver
voltage and frequency where stationary discrete breathers, also known as
intrinsic localized modes (ILM), exist and are stable due to the interplay of
damping and spatially homogeneous driving. By introduc- ing additional
capacitors into the unit cell, these lattices can controllably induce traveling
discrete breathers. When more than one such ILMs are experimentally generated
in the lattice, the interplay of nonlinearity, discreteness and wave
interactions generate a complex dynamics wherein the ILMs attempt to maintain a
minimum distance between one another. Numerical simulations show good agreement
with experimental results, and confirm that these phenomena qualitatively carry
over to larger lattice sizes.Comment: 5 pages, 6 figure
Families of Matter-Waves for Two-Component Bose-Einstein Condensates
We produce several families of solutions for two-component nonlinear
Schr\"{o}dinger/Gross-Pitaevskii equations. These include domain walls and the
first example of an antidark or gray soliton in the one component, bound to a
bright or dark soliton in the other. Most of these solutions are linearly
stable in their entire domain of existence. Some of them are relevant to
nonlinear optics, and all to Bose-Einstein condensates (BECs). In the latter
context, we demonstrate robustness of the structures in the presence of
parabolic and periodic potentials (corresponding, respectively, to the magnetic
trap and optical lattices in BECs).Comment: 6 pages, 4 figures, EPJD in pres
Dark solitons and vortices in PT-symmetric nonlinear media: from spontaneous symmetry breaking to nonlinear PT phase transitions
We consider nonlinear analogues of Parity-Time (PT) symmetric linear systems
exhibiting defocusing nonlinearities. We study the ground state and excited
states (dark solitons and vortices) of the system and report the following
remarkable features. For relatively weak values of the parameter
controlling the strength of the PT-symmetric potential, excited states undergo
(analytically tractable) spontaneous symmetry breaking; as is
further increased, the ground state and first excited state, as well as
branches of higher multi-soliton (multi-vortex) states, collide in pairs and
disappear in blue-sky bifurcations, in a way which is strongly reminiscent of
the linear PT-phase transition ---thus termed the nonlinear PT-phase
transition. Past this critical point, initialization of, e.g., the former
ground state leads to spontaneously emerging solitons and vortices.Comment: 8 pages, 8 figure
Exploring Vortex Dynamics in the Presence of Dissipation: Analytical and Numerical Results
In this paper, we systematically examine the stability and dynamics of
vortices under the effect of a phenomenological dissipation used as a
simplified model for the inclusion of the effect of finite temperatures in
atomic Bose-Einstein condensates. An advantage of this simplified model is that
it enables an analytical prediction that can be compared directly (and
favorably) to numerical results. We then extend considerations to a case of
considerable recent experimental interest, namely that of a vortex dipole and
observe good agreement between theory and numerical computations in both the
stability properties (eigenvalues of the vortex dipole stationary states) and
the dynamical evolution of such configurations.Comment: 12 pages, 5 figures, accepted by PR
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Materials’ Methods: NMR in Battery Research
Improving electrochemical energy storage is one of the major issues of our time. The search for new battery materials together with the drive to improve performance and lower cost of existing and new batteries is not without its challenges. Success in these matters is undoubtedly based on first understanding the underlying chemistries of the materials and the relations between the components involved. A combined application of experimental and theoretical techniques has proven to be a powerful strategy to gain insights into many of the questions that arise from the “how do batteries work and why do they fail” challenge. In this Review, we highlight the application of solid-state nuclear magnetic resonance (NMR) spectroscopy in battery research: a technique that can be extremely powerful in characterizing local structures in battery materials, even in highly disordered systems. An introduction on electrochemical energy storage illustrates the research aims and prospective approaches to reach these. We particularly address “NMR in battery research” by giving a brief introduction to electrochemical techniques and applications as well as background information on both in and ex situ solid-state NMR spectroscopy. We will try to answer the question “Is NMR suitable and how can it help me to solve my problem?” by shortly reviewing some of our recent research on electrodes, microstructure formation, electrolytes and interfaces, in which the application of NMR was helpful. Finally, we share hands-on experience directly from the lab bench to answer the fundamental question “Where and how should I start?” to help guide a researcher’s way through the manifold possible approaches.This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 655444 (O.P.). K.J.G. thanks the Winston Churchill Foundation of the United States and the Herchel Smith Scholarship for financial support
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