797 research outputs found
Radiative Heat Transfer between Neighboring Particles
The near-field interaction between two neighboring particles is known to
produce enhanced radiative heat transfer. We advance in the understanding of
this phenomenon by including the full electromagnetic particle response, heat
exchange with the environment, and important radiative corrections both in the
distance dependence of the fields and in the particle absorption coefficients.
We find that crossed terms of electric and magnetic interactions dominate the
transfer rate between gold and SiC particles, whereas radiative corrections
reduce it by several orders of magnitude even at small separations. Radiation
away from the dimer can be strongly suppressed or enhanced at low and high
temperatures, respectively. These effects must be taken into account for an
accurate description of radiative heat transfer in nanostructured environments.Comment: 22 pages, 9 figures, fully self-contained derivation
Electron energy loss and induced photon emission in photonic crystals
The interaction of a fast electron with a photonic crystal is investigated by
solving the Maxwell equations exactly for the external field provided by the
electron in the presence of the crystal. The energy loss is obtained from the
retarding force exerted on the electron by the induced electric field. The
features of the energy loss spectra are shown to be related to the photonic
band structure of the crystal. Two different regimes are discussed: for small
lattice constants relative to the wavelength of the associated electron
excitations , an effective medium theory can be used to describe the
material; however, for the photonic band structure plays an
important role. Special attention is paid to the frequency gap regions in the
latter case.Comment: 12 pages, 7 figure
Enhanced graphene nonlinear response through geometrical plasmon focusing
We propose a simple approach to couple light into graphene plasmons and focus these excitations at
focal spots of a size determined by the plasmon wavelength, thus producing high optical field
enhancement that boosts the nonlinear response of the material. More precisely, we consider a
graphene structure in which incident light is coupled to its plasmons at the carbon edges and
subsequently focused on a spot of size comparable to the plasmon wavelength. We observe large
confinement of graphene plasmons, materializing in small, intense focal spots, in which the
extraordinary nonlinear response of this material leads to relatively intense harmonic generation.
This result shows the potential of plasmon focusing in suitably edged graphene structures to produce
large field confinement and nonlinear response without involving elaborated nanostructuring.Peer ReviewedPostprint (published version
Magnetic graphene metamaterial
We predict strong magnetic response by graphene split nanorings at THz frequencies allowing to achieve tunable metamaterials with very high (>100) wavelength to unit-cell ratios, not attainable by conventional noble metals
Strong plasmon-phonon splitting and hybridization in 2D materials revealed through a self-energy approach
We reveal new aspects of the interaction between plasmons and phonons in 2D
materials that go beyond a mere shift and increase in plasmon width due to
coupling to either intrinsic vibrational modes of the material or phonons in a
supporting substrate. More precisely, we predict strong plasmon splitting due
to this coupling, resulting in a characteristic avoided crossing scheme. We
base our results on a computationally efficient approach consisting in
including many-body interactions through the electron self-energy. We specify
this formalism for a description of plasmons based upon a tight-binding
electron Hamiltonian combined with the random-phase approximation. This
approach is accurate provided vertex corrections can be neglected, as is is the
case in conventional plasmon-supporting metals and Dirac-fermion systems. We
illustrate our method by evaluating plasmonic spectra of doped graphene
nanotriangles with varied size, where we predict remarkable peak splittings and
other radical modifications in the spectra due to plasmons interactions with
intrinsic optical phonons. Our method is equally applicable to other 2D
materials and provides a simple approach for investigating coupling of plasmons
to phonons, excitons, and other excitations in hybrid thin nanostructures
Multiatom resonant photoemission: Theory and systematics
A first-principles calculation of the recently discovered interatomic multiatom resonant photoemission (MARPE) effect is presented. In this phenomenon, core photoelectron intensities are enhanced when the photon energy is tuned to a core-level absorption edge of nonidentical neighboring atoms, thus enabling direct determination of near-neighbor atomic identities. Both the multiatom character of MARPE and retardation effects in the photon and electron interactions in the resonant channel are shown to be
crucial. Measured peak-intensity enhancements of 40% in MnO and spectral shapes similar to the corresponding x-ray absorption profiles are well reproduced by this theory.This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098, the University of the Basque Country, and the Spanish Ministerio de Educación y Cultura (Fulbright Grant No. FU-98-22726216).Peer reviewe
Robust plasmon waveguides in strongly-interacting nanowire arrays
Arrays of parallel metallic nanowires are shown to provide a tunable, robust,
and versatile platform for plasmon interconnects, including high-curvature
turns with minimum signal loss. The proposed guiding mechanism relies on gap
plasmons existing in the region between adjacent nanowires of dimers and
multi-wire arrays. We focus on square and circular silver nanowires in silica,
for which excellent agreement between both boundary element method and multiple
multipolar expansion calculations is obtained. Our work provides the tools for
designing plasmon-based interconnects and achieving high degree of integration
with minimum cross talk between adjacent plasmon guides.Comment: 4 pages, 5 figure
Temporal Quantum Control with Graphene
We introduce a novel strategy for controlling the temporal evolution of a
quantum system at the nanoscale. Our method relies on the use of graphene
plasmons, which can be electrically tuned in frequency by external gates.
Quantum emitters (e.g., quantum dots) placed in the vicinity of a graphene
nanostructure are subject to the strong interaction with the plasmons of this
material, thus undergoing time variations in their mutual interaction and
quantum evolution that are dictated by the externally applied gating voltages.
This scheme opens a new path towards the realization of quantum-optics devices
in the robust solid-state environment of graphene.Comment: 5 pages, 2 figure
Ultrafast nonlinear optical response of Dirac fermions in graphene
The speed of solid-state electronic devices, determined by the temporal dynamics of charge
carriers, could potentially reach unprecedented petahertz frequencies through direct
manipulation by optical fields, consisting in a million-fold increase from state-of-the-art
technology. In graphene, charge carrier manipulation is facilitated by exceptionally strong
coupling to optical fields, from which stems an important back-action of photoexcited carriers.
Here we investigate the instantaneous response of graphene to ultrafast optical fields,
elucidating the role of hot carriers on sub-100 fs timescales. The measured nonlinear
response and its dependence on interaction time and field polarization reveal the back-action
of hot carriers over timescales commensurate with the optical field. An intuitive picture is
given for the carrier trajectories in response to the optical-field polarization state. We note
that the peculiar interplay between optical fields and charge carriers in graphene may also
apply to surface states in topological insulators with similar Dirac cone dispersion relations.Peer ReviewedPostprint (published version
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