518 research outputs found
Atomic States Entanglement in Carbon Nanotubes
The entanglement of two atoms (ions) doped into a carbon nanotube has been
investigated theoretically. Based on the photon Green function formalism for
quantizing electromagnetic field in the presence of carbon nanotubes,
small-diameter metallic nanotubes are shown to result in a high degree of the
two-qubit atomic entanglement for long times due to the strong atom-field
coupling.Comment: 4 pages, 2 figure
Doubly differential cross sections for ionization of lithium atom by protons and O ions
We consider single ionization of lithium atom in collisions with and
O projectiles. Doubly differential cross sections for ionization are
calculated within a relativistic non-perturbative approach. Comparisons with
the recent measurements and theoretical predictions are made.Comment: Submitted to the Topical Issue of Eur. Phys. J. D based on the
contributions reported on the International Conference on Many Particle
Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS 2018), Budapest,
Hungary, 21-24 August 201
Spontaneous decay of excited atomic states near a carbon nanotube
Spontaneous decay process of an excited atom placed inside or outside (near
the surface) a carbon nanotube is analyzed. Calculations have been performed
for various achiral nanotubes. The effect of the nanotube surface has been
demonstrated to dramatically increase the atomic spontaneous decay rate -- by 6
to 7 orders of magnitude compared with that of the same atom in vacuum. Such an
increase is associated with the nonradiative decay via surface excitations in
the nanotube.Comment: 8 pages, 3 figure
Strong exciton-plasmon coupling in semiconducting carbon nanotubes
We study theoretically the interactions of excitonic states with surface
electromagnetic modes of small-diameter (~1 nm) semiconducting single-walled
carbon nanotubes. We show that these interactions can result in strong
exciton-surface-plasmon coupling. The exciton absorption line shape exhibits
Rabi splitting ~0.1 eV as the exciton energy is tuned to the nearest interband
surface plasmon resonance of the nanotube. We also show that the quantum
confined Stark effect may be used as a tool to control the exciton binding
energy and the nanotube band gap in carbon nanotubes in order, e.g., to bring
the exciton total energy in resonance with the nearest interband plasmon mode.
The exciton-plasmon Rabi splitting we predict here for an individual carbon
nanotube is close in its magnitude to that previously reported for hybrid
plasmonic nanostructures artificially fabricated of organic semiconductors on
metallic films. We expect this effect to open up paths to new tunable
optoelectronic device applications of semiconducting carbon nanotubes.Comment: 22 pages, 8 figures, accepted for PR
Relativistic calculations of the U91+(1s)-U92+ collision using the finite basis set of cubic Hermite splines on a lattice in coordinate space
A new method for solving the time-dependent two-center Dirac equation is
developed. The approach is based on the using of the finite basis of cubic
Hermite splines on a three-dimensional lattice in the coordinate space. The
relativistic calculations of the excitation and charge-transfer probabilities
in the U91+(1s)-U92+ collisions in two and three dimensional approaches are
performed. The obtained results are compared with our previous calculations
employing the Dirac-Sturm basis sets [I.I. Tupitsyn et al., Phys. Rev. A 82,
042701 (2010)]. The role of the negative-energy Dirac spectrum is investigated
within the monopole approximation
van der Waals coupling in atomically doped carbon nanotubes
We have investigated atom-nanotube van der Waals (vdW) coupling in atomically
doped carbon nanotubes (CNs). Our approach is based on the perturbation theory
for degenerated atomic levels, thus accounting for both weak and strong
atom-vacuum-field coupling. The vdW energy is described by an integral equation
represented in terms of the local photonic density of states (DOS). By solving
it numerically, we demonstrate the inapplicability of standard
weak-coupling-based vdW interaction models in a close vicinity of the CN
surface where the local photonic DOS effectively increases, giving rise to an
atom-field coupling enhancement. An inside encapsulation of atoms into the CN
has been shown to be energetically more favorable than their outside adsorption
by the CN surface. If the atom is fixed outside the CN, the modulus of the vdW
energy increases with the CN radius provided that the weak atom-field coupling
regime is realized (i.e., far enough from the CN). For inside atomic position,
the modulus of the vdW energy decreases with the CN radius, representing a
general effect of the effective interaction area reduction with lowering the CN
curvature.Comment: 15 pages, 5 figure
Spontaneous decay dynamics in atomically doped carbon nanotubes
We report a strictly non-exponential spontaneous decay dynamics of an excited
two-level atom placed inside or at different distances outside a carbon
nanotube (CN). This is the result of strong non-Markovian memory effects
arising from the rapid variation of the photonic density of states with
frequency near the CN. The system exhibits vacuum-field Rabi oscillations, a
principal signature of strong atom-vacuum-field coupling, when the atom is
close enough to the nanotube surface and the atomic transition frequency is in
the vicinity of the resonance of the photonic density of states. Caused by
decreasing the atom-field coupling strength, the non-exponential decay dynamics
gives place to the exponential one if the atom moves away from the CN surface.
Thus, atom-field coupling and the character of the spontaneous decay dynamics,
respectively, may be controlled by changing the distance between the atom and
CN surface by means of a proper preparation of atomically doped CNs. This opens
routes for new challenging nanophotonics applications of atomically doped CN
systems as various sources of coherent light emitted by dopant atoms.Comment: 10 pages, 4 figure
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