85,463 research outputs found
Universal Features of the Time Evolution of Evanescent Modes in a Left-Handed Perfect Lens
The time evolution of evanescent modes in Pendry's perfect lens proposal for
ideally lossless and homogeneous, left-handed materials is analyzed. We show
that time development of sub-wavelength resolution exhibits universal features,
independent of model details. This is due to the unavoidable near-degeneracy of
surface electromagnetic modes in the deep sub-wavelength region. By means of a
mechanical analog, it is shown that an intrinsic time scale (missed in
stationary studies) has to be associated with any desired lateral resolution. A
time-dependent cut-off length emerges, removing the problem of divergences
claimed to invalidate Pendry's proposal.Comment: 4 pages, 3 figures, title slightly changed, reference added, minor
correction
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
Effects of extended impurity perturbation in d-wave superconductor
We describe the effects of electronic perturbation distributed on nearest
neighbor sites to the impurity center in a planar \textit{d}-wave
superconductor, in approximation of circular Fermi surface. Alike the behavior
previously reported for point-like perturbation and square Fermi surface, the
quasiparticle density of states can display a resonance
inside the gap (and very weak features from low symmetry representations of
non-local perturbation) and asymptotically vanishes at as
. The local suppression of SC order parameter
in this model is found to be somewhat weaker than for an equivalent point-like
(non-magnetic) perturbation and much weaker than for a spin-dependent
(extended) perturbation.Comment: 7 pages, 5 figures, some minor typos and the curves in Fig. 5
correcte
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