69,799 research outputs found
Plasmons and near-field amplification in double-layer graphene
We study the optical properties of double-layer graphene for linearly
polarized evanescent modes and discuss the in-phase and out-of-phase plasmon
modes for both, longitudinal and transverse polarization. We find a energy for
which reflection is zero, leading to exponentially amplified transmitted modes
similar to what happens in left-handed materials. For layers with equal
densities cm, we find a typical layer separation of
m to detect this amplification for transverse polarization
which may serve as an indirect observation of transverse plasmons. When the two
graphene layers lie on different chemical potentials, the exponential
amplification either follows the in-phase or out-of-phase plasmon mode
depending on the order of the low- and high-density layer. This opens up the
possibility of a tunable near-field amplifier or switch.Comment: 9 pages, 8 figure
Mesoscopic ensembles of polar bosons in triple-well potentials
Mesoscopic dipolar Bose gases in triple-well potentials offer a minimal
system for the analysis of the long-range character of the dipole-dipole
interactions. We show that this long-range character may be clearly revealed by
a variety of possible ground-state phases. In addition, an appropriate control
of short-range and dipolar interactions may lead to novel scenarios for the
dynamics of atoms and polar molecules in lattices, including the dynamical
creation of mesoscopic Schr\"odinger cats, which may be employed as a source of
highly-nonclassical states for Heisenberg-limited interferometry.Comment: 4 pages, 3 figures. Identical to the published version, including
supplemental material (4 pages, 6 figures)
Contact values of the radial distribution functions of additive hard-sphere mixtures in d dimensions: A new proposal
The contact values of the radial distribution functions
of a -dimensional mixture of (additive) hard spheres are considered. A
`universality' assumption is put forward, according to which
, where is a common function for all
the mixtures of the same dimensionality, regardless of the number of
components, is the packing fraction of the mixture, and is a
dimensionless parameter that depends on the size distribution and the diameters
of spheres and . For , this universality assumption holds for the
contact values of the Percus--Yevick approximation, the Scaled Particle Theory,
and, consequently, the Boublik--Grundke--Henderson--Lee--Levesque
approximation. Known exact consistency conditions are used to express
, , and in terms of the radial distribution
at contact of the one-component system. Two specific proposals consistent with
the above conditions (a quadratic form and a rational form) are made for the
-dependence of . For one-dimensional systems, the proposals for
the contact values reduce to the exact result. Good agreement between the
predictions of the proposals and available numerical results is found for
, 3, 4, and 5.Comment: 10 pages, 11 figures; Figure 1 changed; Figure 5 is new; New
references added; accepted for publication in J. Chem. Phy
Plasmonics in topological insulators: Spin-charge separation, the influence of the inversion layer, and phonon-plasmon coupling
We demonstrate via three examples that topological insulators (TI) offer a
new platform for plasmonics. First, we show that the collective excitations of
a thin slab of a TI display spin-charge separation. This gives rise to purely
charge-like optical and purely spin-like acoustic plasmons, respectively.
Second, we argue that the depletion layer mixes Dirac and Schr\"odinger
electrons which can lead to novel features such as high modulation depths and
interband plasmons. The analysis is based on an extension of the usual formula
for optical plasmons that depends on the slab width and on the dielectric
constant of the TI. Third, we discuss the coupling of the TI surface phonons to
the plasmons and find strong hybridisation especially for samples with large
slab widths.Comment: 37 pages, 7 figure
- âŠ