370 research outputs found
The fine structure of microwave-induced magneto-oscillations in photoconductivity of the two-dimensional electron system formed on a liquid-helium surface
The influence of the inelastic nature of electron scattering by surface
excitations of liquid helium (ripplons) on the shape of magnetoconductivity
oscillations induced by resonance microwave (MW) excitation is theoretically
studied. The MW field provides a substantial filling of the first excited
surface subband which sparks off inter-subband electron scattering by ripplons.
This scattering is the origin of magneto-oscillations in the momentum
relaxation rate. The inelastic effect becomes important when the energy of a
ripplon involved compares with the collision broadening of Landau levels.
Usually, such a condition is realized only at sufficiently high magnetic
fields. On the contrary, the inelastic nature of inter-subband scattering is
shown to be more important in a lower magnetic field range because of the new
enhancement factor: the ratio of the inter-subband transition frequency to the
cyclotron frequency. This inelastic effect affects strongly the shape of
conductivity oscillations which acquires an additional wavy feature (a mixture
of splitting and inversion) in the vicinity of the level-matching points where
the above noted ratio is close to an integer.Comment: 10 pages 6 figure
Sonoluminescence and collapse dynamics of multielectron bubbles in helium
Multielectron bubbles (MEBs) differ from gas-filled bubbles in that it is the
Coulomb repulsion of a nanometer thin layer of electrons that forces the bubble
open rather than the pressure of an enclosed gas. We analyze the implosion of
MEBs subjected to a pressure step, and find that despite the difference in the
underlying processes the collapse dynamics is similar to that of gas-filled
bubbles. When the MEB collapses, the electrons inside it undergo strong
accelerations, leading to the emission of radiation. This type of
sonoluminescence does not involve heating and ionisation of any gas inside the
bubble. We investigate the conditions necessary to obtain sonoluminescence from
multielectron bubbles and calculate the power spectrum of the emitted
radiation.Comment: 6 figure
Effect of boundary conditions on the character of ambipolar diffusion in electrolytes
PREInternational audienceWe discuss the details of ambipolar relaxation of the electric field in liquid asymmetric electrolytes to its stationary value. It is demonstrated that the account for finite boundary conditions modifies the existing concepts of this diffusion process. In particular, we succeeded to suggest a qualitatively correct explanation of the observed distribution of the electric fields over the bulk of the cuvette and its nonmonotonic behavior in measurements on the finite-size cuvette. We analyze the conditions of such an anomaly at the intermediate stages of the relaxation proces
Photon-assisted scattering and magnetoconductivity oscillations in a strongly correlated 2D electron system formed on the surface of liquid helium
The influence of strong internal forces on photon-assisted scattering and on
the displacement mechanism of magnetoconductivity oscillations in a
two-dimensional (2D) electron gas is theoretically studied. The theory is
applied to the highly correlated system of surface electrons on liquid helium
under conditions that the microwave frequency is substantially different from
inter-subband resonance frequencies. A strong dependence of the amplitude of
magnetoconductivity oscillations on the electron density is established. The
possibility of experimental observation of such oscillations caused by
photon-assisted scattering is discussed.Comment: 7 pages, 1 figur
On dissociation in weakly doped ice
Currently, there is some ambiguity in the problem of decay of a single donor into charged fragments. Thus, in
the well-known Ostwald approximation used for semiconductors (ice being one of them) the donor dissociation
degree of tends to its maximum value (i.e., unity) as the doping impurity concentration approaches zero. At the
same time, the statistical theory of atom reveals within the Thomas–Fermi (or Debye–Hückel) approximation the
existence of a thermodynamically equilibrium state of a single multi-electron atom (donor) where charged nucleus
keeps the number of counterions just necessary for its neutralization. These scenarios do not show the atom
dissociation at all. Discussed in the present paper is the alternative between the full dissociation of a single donor
(i.e., dissociation degree equals unity) in a semiconducting media (ice, water, semiconductor) and zero dissociation
degree
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