131 research outputs found
QuasiCerenkov Radiation of Relativistic Electrons in Crystals in the Presence of External Excitations
The paper is devoted to the study of the influence of crystalline lattice
distortions due to external excitations (acoustic vibrations, temperature
gradient, etc.) on the Quasicerenkov radiation. Equations describing
Quasicerenkov radiation of charged particles in distorted crystals are derived.
These equations are solved numerically. It is shown that certain types of
lattice deformations may intensify the Quasicerenkov radiation by several
times.Comment: 5 pages,2 figure
Relativistic theory of the above-threshold multiphoton ionization of hydrogen-like atoms in the ultrastrong laser fields
The relativistic theory of above-threshold ionization (ATI) of hydrogen-like
atoms in ultrastrong radiation fields, taking into account the photoelectron
induced rescattering in the continuum spectrum is developed. It is shown that
the contribution of the latter in the multiphoton ionization probability even
in the Born approximation by Coulomb field is of the order of ATI probability
in the scope of Keldysh-Faisal-Reiss ansatz.Comment: REVTeX, 13 page
On the theory of the relativistic cross sections for stimulated bremsstrahlung on an arbitrary electrostatic potential in the strong electromagnetic field
On the base of relativistic generalized eikonal approximation wave function
the multiphoton cross sections of a Dirac particle bremsstrahlung on an
arbitrary electrostatic potential and strong laser radiation field are
presented. In the limit of the Born approximation the ultimate analytical
formulas for arbitrary polarization of electromagnetic wave have been obtained.Comment: Revtex,10 pages,3 figure
Multiphoton Resonant Transitions of Electrons in the Laser Field in a Medium
Within the scope of the relativistic quantum theory for electron-laser
interaction in a medium and using the resonant approximation for the two
degenerated states of an electron in a monochromatic radiation field [1] a
nonperturbative solution of the Dirac equation (nonlinear over field solution
of the Hill type equation) are obtained. The multiphoton cross sections of
electrons coherent scattering on the plane monochromatic wave at the Cherenkov
resonance are obtained taking into account the specificity of induced Cherenkov
process [1, 2] and spin-laser interaction as well. In the result of this
resonant scattering the electron beam quantum modulation at high frequencies
occurs that corresponds to a quantity of an electron energy exchange at the
coherent reflection from the ''phase lattice'' of slowed plane wave in a
medium. So, we can expect to have a coherent X-ray source in induced Cherenkov
process, since such beam is a potential source of coherent radiation itself.Comment: 6 pages, REVTE
Relativistic quantum theory of high harmonic generation on atoms/ions by strong laser fields
High-order harmonic generation (HHG) by hydrogenlike atoms/ions in the
uniform periodic electric field, formed by the two linearly polarized
counterpropagating laser beams of relativistic intensities, is studied. The
relativistic quantum theory of HHG in such fields, at which the impeding factor
of relativistic magnetic drift of a strong wave can be eliminated, is presented
arising from the Dirac equation. Specifically, a scheme of HHG in underdense
plasma with the copropagating ultraintense laser and fast ion beams is
proposed.Comment: 8 pages, 8 figures, Conference: Photons, Atoms, and Qubits 2007
(PAQ07, paper 47
Collective two-boson decay of excitons in Bose-Einstein condensate and generation of coherent photon-phonon radiation
The collective decay of excitons from initial Bose-Einstein condensate state
is investigated theoretically. As practically more interesting case we consider
excitons of the yellow series in the semiconductor cuprous oxide where we have
collective photon and phonon assisted decay of excitons. It is shown that
because of intrinsic instability of recoilless two-boson decay of Bose-Einstein
condensate, the spontaneously emitted bosonic pairs are amplified leading to an
exponential buildup of a macroscopic population into the certain modes. The
collective decay rate has a nonlinear dependence on the excitonic density being
comparable or larger than Auger recombination loss rate up to the high
densities, which makes obtainable its observation. The considering phenomenon
can also be applied for the realization of phonon laser.Comment: 12 pages, 1 figur
Multiphoton interaction of a qutrit with single-mode quantized field in the ultrastrong and deep strong coupling regimes
We consider multiphoton dynamics of a quantum system composed of a
three-state atom (a qutrit) and a single-mode photonic field in the ultrastrong
and deep strong coupling regimes, when the coupling strength is comparable to
or larger than the oscillator energy scale. We assume a qutrit to be in a
polar- configuration in which two lower levels have mean dipole
moments. Direct multiphoton resonant transitions revealing generalized Rabi
oscillations, collapse, and revivals in atomic excitation probabilities for the
ultrastrong couplings are studied. In the deep strong coupling regime
particular emphasis is placed on the ground state of considering system which
exhibits strictly nonclassical properties.Comment: 10 pages, 12 figures, Submitted to Phys. Rev.
Microscopic quantum description of second-order nonlinearities in 2D hexagonal nanostructures beyond the Dirac cone approximation
Single layers of hexagonal two-dimensional nanostructures such as graphene,
silicene, and germanene exhibit large carrier Fermi velocities and,
consequently, large light-matter coupling strength making these materials
promising elements for nano-opto-electronics. Although these materials are
centrosymmetric, the spatial dispersion turns out to be quite large allowing
the second-order nonlinear response of such materials to be comparable to the
non-centrosymmetric 2D ones. The second-order response of massless Dirac
fermions has been extensively studied, however a general approach correct over
the full Brillouin zone is lacking so far. To complete this gap, in the current
paper we develop a general quantum-mechanical theory of the in-plane
second-order nonlinear response beyond the Dirac cone approximation and
applicable to the full Brillouin zone of the hexagonal tight-binding
nanostructures. We present explicit calculation of the nonlinear susceptibility
tensor of 2D hexagonal nanostructures applicable to arbitrary three-wave mixing
processes.Comment: 14 pages, 13 figure
Multiphoton excitation and high-harmonics generation in topological insulator
Multiphoton interaction of coherent electromagnetic radiation with 2D
metallic carriers confined on the surface of the 3D topological insulator is
considered. A microscopic theory describing the nonlinear interaction of a
strong wave and metallic carriers with many-body Coulomb interaction is
developed. The set of integrodifferential equations for the interband
polarization and carrier occupation distribution is solved numerically.
Multiphoton excitation of Fermi-Dirac sea of 2D massless carriers is considered
for a THz pump wave. It is shown that in the moderately strong pump wave field
along with multiphoton interband/intraband transitions the intense radiation of
high harmonics takes place.Comment: 13 pages, 7 figure
Nonlinear absorption of high-intensity shortwave radiation in plasma within relativistic quantum theory
On the base of the quantum kinetic equation for density matrix in plasma at
the stimulated bremsstrahlung of electrons on ions, the nonlinear absorption
rate for high-intensity shortwave radiation in plasma has been obtained within
relativistic quantum theory. Both classical Maxwellian and degenerate quantum
plasma are considered for x-ray lasers of high intensities. Essentially
different dependences of nonlinear absorption rate on polarization of strong
laser radiation is stated.Comment: 8 pages, 9 figure
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