arXiv subjects

Dafei Jin

Publications and source records attributed to Dafei Jin.

42 records · Page 3Linked to original sources

arXiv2014

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.

physics.optics↗

arXiv2013

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.

physics.optics↗

arXiv2013

Ferroelectric-Gated Terahertz Plasmonics on Graphene

Inspired by recent advancement of low-power ferroelectic-gated memories and transistors, we propose a design of ferroelectic-gated nanoplasmonic devices based on graphene sheets clamped in ferroelectric crystals. We show that the two-dimensional plasmons in graphene strongly couple with the phonon-polaritons in ferroelectrics at terahertz frequencies, leading to characteristic modal wavelength of the order of 100--200 nm at only 3--4 THz. By patterning the ferroelectrics into different domains, one can produce compact on-chip plasmonic waveguides, which exhibit negligible crosstalk even at 50 nm separation distance. Harnessing the memory effect of ferroelectrics, low-power electro-optical switching can be achieved on these plasmonic waveguides.

cond-mat.mes-hall↗

arXiv2010

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-bubbles

cond-mat.other↗

arXiv2010

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.

cond-mat.other↗

arXiv2008

Stability of multi-electron bubbles in liquid helium

The stability of multi-electron bubbles in liquid helium is investigated theoretically. We find that multi-electron bubbles are unstable against fission whenever the pressure is positive. It is shown that for moving bubbles the Bernoulli effect can result in a range of pressures over which the bubbles are stable.

cond-mat.other↗