Energy of a single electron in gaseous media

The so-called «optical» approximation in the theory of electron energy spectrum in the presence of scattering centers with positive scattering length randomly distributed with the average density ng is considered for a number of inert gases. The average minimal energy W of a single electron calculated beyond the optical approximation reveals a behavior qualitatively different from that of the same quantity W₀ derived within the optical approximation. Results of calculations are in qualitative agreement with experimental data available for theW(ng) dependence for different cryogenic gases

Shielding characteristics of water

In this article we demonstrate that a relatively small density of intrinsic ions in pure water has a significant impact on the development of the instability of the liquid–vapor boundary in an external electric field perpendicular to the interface. Dielectric breakdown scenario (Shliomis model) is shunted by alternative metal scenario (Frenkel model). Experimentally we observed the formation of a positively charged layer beneath the surface in weak perpendicular electrical fields. In strong electrical fields surface of water loses its stability and charges pass through the interface. Surface discharge process is periodic with a characteristic time of the order of tens seconds

Stationary nonlinear waves at the surface of a thin liquid layer under inverted gravitation conditions

Instability of the flat surface of a thin liquid layer wetting a solid substrate under inverted gravitation conditions is discovered. The development of this instability leads to formation of a new stationary nonuniform liquid surface state. It looks like a solitary hill with characteristics sensitive to the liquid film parameters, particularly to the layer thickness at which the instability begins to develop. By application of a variational approach the mechanical stability of such a hill (droplet) in the one-dimensional approximation is proved. A variational picture of the shape evolution for a cylindrical charged droplet in an external electric field is constructed, too. The results obtained are compared with an experiment on liquid hydrogen droplets [A.A. Levchenko, G.V. Kolmakov, L.P. Mezhov-Deglin, M.G. Mikhailov, and A.B. Trusov, Low Temp. Phys. 25, 242 (1999)]. The theory developed is in good agreement with the results of experiments

Electron transport in a quasi-one dimensional channel on suspended helium films

Quasi-one dimensional electron systems have been created using a suspended helium film on a structured substrate. The electron mobility along the channel is calculated by taking into account the essential scattering processes of electrons by helium atoms in the vapor phase, ripplons, and surface defects of the film substrate. It is shown that the last scattering mechanism may dominate the electron mobility in the low temperature limit changing drastically the temperature dependence of the mobility in comparison with that controlled by the electron-ripplon scattering.Comment: 4 pages, 1 figur

Fission of multielectron bubbles in liquid helium

The stability of multielectron bubbles (MEBs) in liquid helium is investigated using the liquid-drop model for fissioning nuclei. Whereas a critical positive pressure can make the bubble unstable against fissioning, a small negative pressure suffices to introduce a restoring force preventing any small deformation of the bubble to grow. We also find that there exists an energy barrier making MEBs metastable against fissioning at zero pressure. The results obtained here overcome the difficulties associated with the Rayleigh-Plesset equation previously used to study bubble stability, and shed new light on the limits of achievable bubble geometries in recently proposed experiments devised to stabilize MEBs.Comment: 11 pages and 5 figures, accepted in Phys. Rev.

Magnetoresistance of nondegenerate quantum electron channels formed on the surface of superfluid helium

Transport properties of quasi-one-dimensional nondegenerate quantum wires formed on the surface of liquid helium in the presence of a normal magnetic field are studied using the momentum balance equation method and the memory function formalism. The interaction with both kinds of scatterers available (vapor atoms and capillary wave quanta) is considered. We show that unlike classical wires, quantum nondegenerate channels exhibit strong magnetoresistance which increases with lowering the temperature.Comment: 8 pages, 7 figure

Spontaneous Coherence and Collective Modes in Double-Layer Quantum Dot Systems

We study the ground state and the collective excitations of parabolically-confined double-layer quantum dot systems in a strong magnetic field. We identify parameter regimes where electrons form maximum density droplet states, quantum-dot analogs of the incompressible states of the bulk integer quantum Hall effect. In these regimes the Hartree-Fock approximation and the time-dependent Hartree-Fock approximations can be used to describe the ground state and collective excitations respectively. We comment on the relationship between edge excitations of dots and edge magneto-plasmon excitations of bulk double-layer systems.Comment: 20 pages (figures included) and also available at http://fangio.magnet.fsu.edu/~jhu/Paper/qdot_cond.ps, replaced to fix figure

Decoherence in trapped ions due to polarization of the residual background gas

We investigate the mechanism of damping and heating of trapped ions associated with the polarization of the residual background gas induced by the oscillating ions themselves. Reasoning by analogy with the physics of surface electrons in liquid helium, we demonstrate that the decay of Rabi oscillations observed in experiments on 9Be+ can be attributed to the polarization phenomena investigated here. The measured sensitivity of the damping of Rabi oscillations with respect to the vibrational quantum number of a trapped ion is also predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum

Surface state atoms and their contribution to the surface tension of quantum liquids

We investigate the new type of excitations on the surface of liquid helium. These excitations, called surfons, appear because helium atoms have discrete energy level at the liquid surface, being attracted to the surface by the van der Waals force and repulsed at a hard-core interatomic distance. The concentration of the surfons increases with temperature. The surfons propagate along the surface and form a two-dimensional gas. Basing on the simple model of the surfon microscopic structure, we estimate the surfon activation energy and effective mass for both helium isotopes. We also calculate the contribution of the surfons to the temperature dependence of the surface tension. This contribution explains the great and long-standing discrepancy between theory and experiment on this temperature dependence in both helium isotopes. The achieved agreement between our theory and experiment is extremely high. The comparison with experiment allows to extract the surfon activation energy and effective mass. The values of these surfon microscopic parameters are in a reasonable agreement with the calculated from the proposed simple model of surfon structure.Comment: 10 pages, 6 figure