50 research outputs found
Plasmonic angular momentum on metal-dielectric nano-wedges in a sectorial indefinite metamaterial
We present an analytical study to the structure-modulated plasmonic angular
momentum trapped on periodic metal-dielectric nano-wedges in the core region of
a sectorial indefinite metamaterial. Employing a transfer-matrix calculation
and a conformal-mapping technique, our theory is capable of dealing with
realistic configurations of arbitrary sector numbers and rounded wedge tips. We
demonstrate that in the deep-subwavelength regime strong electric field
carrying high azimuthal variation can exist within only ten-nanometer length
scale close to the structural center, and is naturally bounded by a
characteristic radius of the order of hundred-nanometer away from the center.
These extreme confining properties suggest that the structure under
investigation may be superior to the conventional metal-dielectric waveguides
or cavities in terms of nanoscale photonic manipulation.Comment: 16 pages, 9 figure
Optical Torque from Enhanced Scattering by Multipolar Plasmonic Resonance
We present a theoretical study of the optical angular momentum transfer from
a circularly polarized plane wave to thin metal nanoparticles of different
rotational symmetries. While absorption has been regarded as the predominant
mechanism of torque generation on the nanoscale, we demonstrate numerically how
the contribution from scattering can be enhanced by using multipolar plasmon
resonance. The multipolar modes in non-circular particles can convert the
angular momentum carried by the scattered field, thereby producing
scattering-dominant optical torque, while a circularly symmetric particle
cannot. Our results show that the optical torque induced by resonant scattering
can contribute to 80% of the total optical torque in gold particles. This
scattering-dominant torque generation is extremely mode-specific, and deserves
to be distinguished from the absorption-dominant mechanism. Our findings might
have applications in optical manipulation on the nanoscale as well as new
designs in plasmonics and metamaterials.Comment: main article 20 pages, 4 figures; supplementary material 6 pages, 2
figure
Vortex Nucleation Induced Phonon Radiation from a Moving Electron Bubble in Superfluid 4He
We construct an efficient zero-temperature semi-local density functional to
dynamically simulate an electron bubble passing through superfluid 4He under
various pressures and electric fields up to nanosecond timescale. Our simulated
drift velocity can be quantitatively compared to experiments particularly when
pressure approaches zero. We find that the high-speed bubble experiences
remarkable expansion and deformation before vortex nucleation occurs.
Accompanied by vortex-ring shedding, drastic surface vibration is generated
leading to intense phonon radiation into the liquid. The amount of energy
dissipated by these phonons is found to be greater than the amount carried away
solely by the vortex rings. These results may enrich our understanding about
the vortex nucleation induced energy dissipation in this fascinating system.Comment: 7 pages, 5 figure
Excited electron-bubble states in superfluid helium-4: a time-dependent density functional approach
We present a systematic study on the excited electron-bubble states in
superfluid helium-4 using a time-dependent density functional approach. For the
evolution of the 1P bubble state, two different functionals accompanied with
two different time-development schemes are used, namely an accurate
finite-range functional for helium with an adiabatic approximation for electron
versus an efficient zero-range functional for helium with a real-time evolution
for electron. We make a detailed comparison between the quantitative results
obtained from the two methods, which allows us to employ with confidence the
optimal method for suitable problems. Based on this knowledge, we use the
finite-range functional to calculate the time-resolved absorption spectrum of
the 1P bubble, which in principle can be experimentally determined, and we use
the zero-range functional to real-time evolve the 2P bubble for several
hundreds of picoseconds, which is theoretically interesting due to the break
down of adiabaticity for this state. Our results discard the physical
realization of relaxed, metastable 2P electron-bubblesComment: 16 pages, 12 figure
Topological magnetoplasmon
Classical wave fields are real-valued, ensuring the wave states at opposite
frequencies and momenta to be inherently identical. Such a particle-hole
symmetry can open up new possibilities for topological phenomena in classical
systems. Here we show that the historically studied two-dimensional (2D)
magnetoplasmon, which bears gapped bulk states and gapless one-way edge states
near zero frequency, is topologically analogous to the 2D topological p+\Ii p
superconductor with chiral Majorana edge states and zero modes. We further
predict a new type of one-way edge magnetoplasmon at the interface of opposite
magnetic domains, and demonstrate the existence of zero-frequency modes bounded
at the peripheries of a hollow disk. These findings can be readily verified in
experiment, and can greatly enrich the topological phases in bosonic and
classical systems.Comment: 12 pages, 6 figures, 1 supporting materia