220 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
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
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
Charged-Surface Instability Development in Liquid Helium; Exact Solutions
The nonlinear dynamics of charged-surface instability development was
investigated for liquid helium far above the critical point. It is found that,
if the surface charge completely screens the field above the surface, the
equations of three-dimensional (3D) potential motion of a fluid are reduced to
the well-known equations describing the 3D Laplacian growth process. The
integrability of these equations in 2D geometry allows the analytic description
of the free-surface evolution up to the formation of cuspidal singularities at
the surface.Comment: latex, 5 pages, no figure
Low-Temperature Mobility of Surface Electrons and Ripplon-Phonon Interaction in Liquid Helium
The low-temperature dc mobility of the two-dimensional electron system
localized above the surface of superfluid helium is determined by the slowest
stage of the longitudinal momentum transfer to the bulk liquid, namely, by the
interaction of surface and volume excitations of liquid helium, which rapidly
decreases with temperature. Thus, the temperature dependence of the
low-frequency mobility is \mu_{dc} = 8.4x10^{-11}n_e T^{-20/3} cm^4 K^{20/3}/(V
s), where n_e is the surface electron density. The relation
T^{20/3}E_\perp^{-3} << 2x10^{-7} between the pressing electric field (in
kV/cm) and temperature (in K) and the value \omega < 10^8 T^5 K^{-5}s^{-1} of
the driving-field frequency have been obtained, at which the above effect can
be observed. In particular, E_\perp = 1 kV/cm corresponds to T < 70 mK and
\omega/2\pi < 30 Hz.Comment: 4 pages, 1 figur
Classical artificial two-dimensional atoms: the Thomson model
The ring configurations for classical two-dimensional atoms are calculated
within the Thomson model and compared with the results from `exact' numerical
simulations. The influence of the functional form of the confinement potential
and the repulsive interaction potential between the particles on the
configurations is investigated. We also give exact results on those eigenmodes
of the system whose frequency does not depend on the number of particles in the
system.Comment: 9 pages, RevTeX, 4 figure
Microwave photoresponse in the 2D electron system caused by intra-Landau level transitions
The influence of microwave radiation on the DC-magnetoresistance of
2D-electrons is studied in the regime beyond the recently discovered zero
resistance states when the cyclotron frequency exceeds the radiation frequency.
Radiation below 30 GHz causes a strong suppression of the resistance over a
wide magnetic field range, whereas higher frequencies produce a non-monotonic
behavior in the damping of the Shubnikov-de Haas oscillations. These
observations are explained by the creation of a non-equilibrium electron
distribution function by microwave induced intra-Landau level transitions.Comment: 4 pages, 5 figure
Stability of multi-electron bubbles in liquid helium
The stability of multi-electron bubbles in liquid helium is investigated
theoretically. We find that multi-electron bubbles are unstable against fission
whenever the pressure is positive. It is shown that for moving bubbles the
Bernoulli effect can result in a range of pressures over which the bubbles are
stable.Comment: 7 pages, 5 figure
Conformal mapping and shot noise in graphene
Ballistic transport through a collection of quantum billiards in undoped
graphene is studied analytically within the conformal mapping technique. The
billiards show pseudodiffusive behavior, with the conductance equal to that of
a classical conductor characterized by the conductivity ,
and the Fano factor . By shrinking at least one of the billiard
openings, we observe a tunneling behavior, where the conductance shows a
power-law decay with the system size, and the shot noise is Poissonian (F=1).
In the crossover region between tunneling and pseudodiffusive regimes, the
conductance . The degeneracy for the Corbino
disk, which preserves the full symmetry of the Dirac equation, for
billiards bounded with smooth edges which break the symplectic symmetry, and
when abrupt edges lead to strong intervalley scattering. An alternative,
analytical or numerical technique, is utilized for each of the billiards to
confirm the applicability of the conformal mapping for various boundary
conditions.Comment: RevTeX, 16 pages, 15 figure
Absolute Negative Conductivity in Two-Dimensional Electron Systems Associated with Acoustic Scattering Stimulated by Microwave Radiation
We discuss the feasibility of absolute negative conductivity (ANC) in
two-dimensional electron systems (2DES) stimulated by microwave radiation in
transverse magnetic field. The mechanism of ANC under consideration is
associated with the electron scattering on acoustic piezoelectric phonons
accompanied by the absorption of microwave photons. It is demonstrated that the
dissipative components of the 2DES dc conductivity can be negative
() when the microwave frequency is
somewhat higher than the electron cyclotron frequency or its
harmonics. The concept of ANC associated with such a scattering mechanism can
be invoked to explain the nature of the occurrence of zero-resistance
``dissipationless'' states observed in recent experiments.Comment: 7 pager, 2 figure
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