294 research outputs found
Electromagnetic Wave Transmission Through a Subwavelength Nano-hole in a Two-dimensional Plasmonic Layer
An integral equation is formulated to describe electromagnetic wave
transmission through a sub-wavelength nano-hole in a thin plasmonic sheet in
terms of the dyadic Green's function for the associated Helmholtz problem.
Taking the subwavelength radius of the nano-hole to be the smallest length of
the system, we have obtained an exact solution of the integral equation for the
dyadic Green's function analytically and in closed form. This dyadic Green's
function is then employed in the numerical analysis of electromagnetic wave
transmission through the nano-hole for normal incidence of the incoming wave
train. The electromagnetic transmission involves two distinct contributions,
one emanating from the nano-hole and the other is directly transmitted through
the thin plasmonic layer itself (which would not occur in the case of a perfect
metal screen). The transmitted radiation exhibits interference fringes in the
vicinity of the nano-hole, and they tend to flatten as a function of increasing
lateral separation from the hole, reaching the uniform value of transmission
through the sheet alone at large separations.Comment: 14 pages, 24 individual figures organized in 9 captioned group
Elimination of negative differential conductance in an asymmetric molecular transistor by an ac-voltage
We analyze resonant tunneling subject to a non-adiabatic time-dependent
bias-voltage through an asymmetric single molecular quantum dot with coupling
between the electronic and vibrational degrees of freedom using a {\em
Tien-Gordon-type} rate equation. Our results clearly exhibit the appearance of
photon-assisted satellites in the current-voltage characteristics and the
elimination of hot-phonon-induced negative differential conductance with
increasing ac driving amplitude for an asymmetric system. This can be ascribed
to an {\em ac-induced suppression} of unequilibrated (hot) phonons in an
asymmetric system.Comment: Accepted by Appl. Phys. Let
Finite-frequency current (shot) noise in coherent resonant tunneling through a coupled-quantum-dot interferometer
We examine the shot noise spectrum properties of coherent resonant tunneling
in coupled quantum dots in both series and parallel arrangements by means of
quantum rate equations and MacDonald's formula. Our results show that, for a
series-CQD with a relatively high dot-dot hopping ,
( denotes the dot-lead tunnel-coupling
strength), the noise spectrum exhibits a dip at the Rabi frequency, ,
in the case of noninteracting electrons, but the dip is supplanted by a peak in
the case of strong Coulomb repulsion; furthermore, it becomes a dip again for a
completely symmetric parallel-CQD by tuning enclosed magnetic-flux.Comment: 8 pages, 5 figure
Coulomb drag in double quantum wells with a perpendicular magnetic field
Momentum transfer due to electron-electron interaction (Coulomb drag) between
two quantum wells, separated by a distance , in the presence of a
perpendicular magnetic field, is studied at low temperatures. We find besides
the well known Shubnikov-de Haas oscillations, which also appear in the drag
effect, the momentum transfer is markedly enhanced by the magnetic field.Comment: 8 pages, Revtex, 4 Postscript figures are available upon request,
Accepted by Mod. Phys. Lett.
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