58 research outputs found
Lifetime of the surface magnetoplasmons in metallic nanoparticles
We study the influence of an external magnetic field on the collective
electronic excitations in metallic nanoparticles. While the usual surface
plasmon corresponding to the collective oscillation of the electrons with
respect to the ionic background persists in the direction parallel to the
magnetic field, the components in the perpendicular plane are affected by the
field and give rise to two collective modes with field-dependent frequencies,
the surface magnetoplasmons. We analyze the decay of these collective
excitations by their coupling to particle-hole excitations and determine how
their lifetimes are modified by the magnetic field. In particular, we show that
the lifetime of the usual surface plasmon is not modified by the magnetic
field, while the lifetime of the two surface magnetoplasmons present a weak
magnetic-field dependence. Optical spectroscopy experiments are suggested in
which signatures of the surface magnetoplasmons may be observed.Comment: 11 pages, 6 figures; published versio
Transmission phase of a quantum dot and statistical fluctuations of partial-width amplitudes
Experimentally, the phase of the amplitude for electron transmission through
a quantum dot (transmission phase) shows the same pattern between consecutive
resonances. Such universal behavior, found for long sequences of resonances, is
caused by correlations of the signs of the partial-width amplitudes of the
resonances. We investigate the stability of these correlations in terms of a
statistical model. For a classically chaotic dot, the resonance eigenfunctions
are assumed to be Gaussian distributed. Under this hypothesis, statistical
fluctuations are found to reduce the tendency towards universal phase
evolution. Long sequences of resonances with universal behavior only persist in
the semiclassical limit of very large electron numbers in the dot and for
specific energy intervals. Numerical calculations qualitatively agree with the
statistical model but quantitatively are closer to universality.Comment: 8 pages, 4 figure
Decay of dark and bright plasmonic modes in a metallic nanoparticle dimer
We develop a general quantum theory of the coupled plasmonic modes resulting
from the near-field interaction between localized surface plasmons in a
heterogeneous metallic nanoparticle dimer. In particular, we provide analytical
expressions for the frequencies and decay rates of the bright and dark
plasmonic modes. We show that, for sufficiently small nanoparticles, the main
decay channel for the dark plasmonic mode, which is weakly coupled to light
and, hence, immune to radiation damping, is of nonradiative origin and
corresponds to Landau damping, i.e., decay into electron-hole pairs.Comment: 9 pages, 3 figures; published versio
Surface plasmon in metallic nanoparticles: renormalization effects due to electron-hole excitations
The electronic environment causes decoherence and dissipation of the
collective surface plasmon excitation in metallic nanoparticles. We show that
the coupling to the electronic environment influences the width and the
position of the surface plasmon resonance. A redshift with respect to the
classical Mie frequency appears in addition to the one caused by the spill-out
of the electronic density outside the nanoparticle. We characterize the
spill-out effect by means of a semiclassical expansion and obtain its
dependence on temperature and the size of the nanoparticle. We demonstrate that
both, the spill-out and the environment-induced shift are necessary to explain
the experimentally observed frequencies and confirm our findings by
time-dependent local density approximation calculations of the resonance
frequency. The size and temperature dependence of the environmental influence
results in a qualitative agreement with pump-probe spectroscopic measurements
of the differential light transmission.Comment: 15 pages, 8 figures; version accepted in PR
Topological plasmons in dimerized chains of nanoparticles: robustness against long-range quasistatic interactions and retardation effects
We present a simple model of collective plasmons in a dimerized chain of
spherical metallic nanoparticles, an elementary example of a topologically
nontrivial nanoplasmonic system. Taking into account long-range quasistatic
dipolar interactions throughout the chain, we provide an exact analytical
expression for the full quasistatic bandstructure of the collective plasmons.
An explicit calculation of the Zak phase proves the robustness of the
topological physics of the system against the inclusion of long-range Coulomb
interactions, despite the broken chiral symmetry. Using an open quantum systems
approach, which includes retardation through the plasmon-photon coupling, we go
on to analytically evaluate the resulting radiative frequency shifts of the
plasmonic spectrum. The bright plasmonic bands experience size-dependent
radiative shifts, while the dark bands are essentially unaffected by the
light-matter coupling. Notably, the upper transverse-polarized band presents a
logarithmic singularity where the quasistatic spectrum intersects the light
cone. At wavevectors away from this intersection and for subwavelength
nanoparticles, the plasmon-photon coupling only leads to a quantitative
reconstruction of the bandstructure and the topologically-protected states at
the edge of the first Brillouin zone are essentially unaffected.Comment: 15 pages, 6 figures, published versio
Nonradiative limitations to plasmon propagation in chains of metallic nanoparticles
We investigate the collective plasmonic modes in a chain of metallic
nanoparticles that are coupled by near-field interactions. The size- and
momentum-dependent nonradiative Landau damping and radiative decay rates are
calculated analytically within an open quantum system approach. These decay
rates determine the excitation propagation along the chain. In particular, the
behavior of the radiative decay rate as a function of the plasmon wavelength
leads to a transition from an exponential decay of the collective excitation
for short distances to an algebraic decay for large distances. Importantly, we
show that the exponential decay is of a purely nonradiative origin. Our
transparent model enables us to provide analytical expressions for the
polarization-dependent plasmon excitation profile along the chain and for the
associated propagation length. Our theoretical analysis constitutes an
important step in the quest for the optimal conditions for plasmonic
propagation in nanoparticle chains.Comment: 14 pages, 6 figures; v2: published versio
Manipulating type-I and type-II Dirac polaritons in cavity-embedded honeycomb metasurfaces
Pseudorelativistic Dirac quasiparticles have emerged in a plethora of
artificial graphene systems that mimic the underlying honeycomb symmetry of
graphene. However, it is notoriously difficult to manipulate their properties
without modifying the lattice structure. Here we theoretically investigate
polaritons supported by honeycomb metasurfaces and, despite the trivial nature
of the resonant elements, we unveil rich Dirac physics stemming from a
non-trivial winding in the light-matter interaction. The metasurfaces
simultaneously exhibit two distinct species of massless Dirac polaritons,
namely type-I and type-II. By modifying only the photonic environment via an
enclosing cavity, one can manipulate the location of the type-II Dirac points,
leading to qualitatively different polariton phases. This enables one to alter
the fundamental properties of the emergent Dirac polaritons while preserving
the lattice structure - a unique scenario which has no analog in real or
artificial graphene systems. Exploiting the photonic environment will thus give
rise to unexplored Dirac physics at the subwavelength scale
Euler buckling instability and enhanced current blockade in suspended single-electron transistors
Single-electron transistors embedded in a suspended nanobeam or carbon
nanotube may exhibit effects originating from the coupling of the electronic
degrees of freedom to the mechanical oscillations of the suspended structure.
Here, we investigate theoretically the consequences of a capacitive
electromechanical interaction when the supporting beam is brought close to the
Euler buckling instability by a lateral compressive strain. Our central result
is that the low-bias current blockade, originating from the electromechanical
coupling for the classical resonator, is strongly enhanced near the Euler
instability. We predict that the bias voltage below which transport is blocked
increases by orders of magnitude for typical parameters. This mechanism may
make the otherwise elusive classical current blockade experimentally
observable.Comment: 15 pages, 10 figures, 1 table; published versio
Large current noise in nanoelectromechanical systems close to continuous mechanical instabilities
We investigate the current noise of nanoelectromechanical systems close to a
continuous mechanical instability. In the vicinity of the latter, the
vibrational frequency of the nanomechanical system vanishes, rendering the
system very sensitive to charge fluctuations and, hence, resulting in very
large (super-Poissonian) current noise. Specifically, we consider a suspended
single-electron transistor close to the Euler buckling instability. We show
that such a system exhibits an exponential enhancement of the current noise
when approaching the Euler instability which we explain in terms of telegraph
noise.Comment: 11 pages, 12 figures; v2: minor changes, published versio
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