The influence of an electric field on ferroelectric-antiferroelectric frustration in smectics

A microscopic theory describing smectic phases frustrated between ferroelectric and antiferroelectric states is generalized to the case where an external electric field is present. It is shown that two threshold values of the electric field. The first one corresponds to helix unwinding, while the second corresponds to destruction of the phase with frustrated elementary cells. The obtained theoretical conclusions are compared with the experimental results.     

Surface states in an external electric field

In an electric field typical for field ion microscopy, true surface states can exist. Their shift towards higher energies can be quite significant, and moreover, additional surface levels at still higher energies can appear.     

Threshold effects in homeotropically oriented nematic liquid crystals in an external electric field

The electric field-induced orientational transition in a homeotropically oriented nematic liquid crystal cell is investigated. The interaction with the field as a result of anisotropy of the permittivity and flexoelectric polarization is taken into account. For an arbitrary energy of interaction of the nematic with the substrate simple relations are derived for determining the threshold characteristics of the phase transition. It is shown that, in contrast with planar orientation, in fields above a critical value a periodic structure can occur only by virtue of the flexoelectric effect. The resulting dependences for the threshold parameters in the given geometry are exceptionally useful for determining experimentally the surface energy and the difference in the flexoelectric coefficients. Zh. éksp. Teor. Fiz. 116, 543–550 (August 1999)     

Controllable dissipative tunneling in an external electric field

We have studied the problem of controllable dissipative tunneling in the system of tunnel-binding quantum dots (quantum molecules) and in the “AFM/STM cantilever tip-quantum dot” system, which was simulated by a double-well oscillator potential interacting with a heat-bath in an external electric field. We show that theoretical results qualitatively describe some experimental I–V curves for “the AFM/STM cantilever tip-zirconium quantum dot” system. These experimental curves were obtained in the Research Institute of Physics and Technologies at the State University of Nizhniy Novgorod.     

Observed two-dimensional tunnel bifurcations in an external electric field

The controllability problem for two-dimensional dissipative tunneling in the system of tunnel-coupled quantum dots (a quantum molecule), interacting quantum molecules, and the system “ACM/CTM cantilever tip-quantum dot” simulated by a 2D oscillator potential in a heat bath and an external electric field is investigated. The obtained results qualitatively correspond to the separate experimental volt-ampere characteristics (VACs) for the system “platinized ACM/CTM cantilever tip-gold quantum dot” obtained at Scientific-Research Physical-Technical Institute with Nizhnii Novgorod State University. The previously-predicted 2D tunnel bifurcations with dissipation for the case of interacting particles tunneling in parallel are found to be experimentally observed and stable.     

The rotating two-electron atom in an external electric field

Three rigid-body solutions for a rotating two-electron atom under the influence of an electric field along the rotation axis have been obtained within a classical approach. One exact solution gives in the zero-field case a previous result known as a rotor, another exact solution in the zero-field case gives the Wannier unbound solution, and a numerical solution in the zero-field case gives the asymmetric top or Langmuir solution. The stability analysis of the linearized motions around each of the equilibrium configurations was made for different values of the electric field. We find critical values of the electric field beyond which no equilibrium exists. Values for the classical polarizability of rotating H^– and He are reported.     

Surface superconductivity induced by an external electric field

A theory of surface superconductivity induced by an external electric field in superconducting semimetals, metals and semiconductors is presented. It is shown that the inhomogeneous surface superconducting state deeply penetrates into the bulk of the sample. The dependence of the critical surface temperature and magnetic field on the external electric field is calculated.     

Optical absorption by piezopolarons in an external static electric field

The infrared optical absorption by piezopolarons in the presence of a weak external static electric field is analysed (electron-phonon coupling α = 5).     

Bremsstrahlung produced by colliding particles in an external electric field

We have used the nonrelativistic dipole Born approximation to study bremsstrahlung from two colliding charged particles in a uniform electric field. We have calculated the differential cross sections for photon emission as the system transitions into various states of internal motion. We find the cross sections exhibit spatial anisotropy due to the uniform electric field, and that oscillations can arise that are probably due to interference effects between the colliding particles.Khabarovskii State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 46–50, July, 1994.     

Potential gradient along semiconductor-surface projections in an external electric field

The potential gradient is calculated as a function of the external magnetic field for a semiconductor surface in the form spatially periodic rectangular projections and indentations. Cases of projections that are much larger than and comparable with the electric-field shielding length are examined. it is shown that the functions have a maximum, whose magnitude and location are determined by the relationship between the electron and hole concentration and the surface profile and the relationship between the projection dimensions and the electric-field shielding length.Kharkov Institute of Radio Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 36, No. 11, pp. 985–994, November, 1993.     

Event-driven simulations of insulating grains in an external electric field

In this work we employ event-driven particle dynamics simulations for a system of spherical insulating grains interacting with an external electric field. This system resembles the electrostatic particle separation present on some industrial processes. Here, the particles collide inelastically with each other and with the container walls, for a constant normal and tangential restitution coefficients. During the collisions, the grains can acquire electric charge due to triboelectric contact charging, since two different species of insulating particles are mixed. Particle-particle electric interactions are not considered. Grains are also subjected to the gravitational field and rotation, and are confined in a cubic box with thermal walls in order to prevent the static equilibrium state. We calculate the mass and charge density profile, and the particle charge distribution for different values of the electric field and temperature of the walls. The particle charge distribution and the effect of particle sizes on the separation process were also investigated.     

Solitons in photovoltaic photorefractive media with an external electric field

We use the classical Lie-group method for studying the evolution equation in photovoltaic photorefractive media with an external electric field, reducing it to some similarity equations firstly, and then obtain some exact analytical solutions including the soliton solution, the period solution and the oscillatory solution. We also obtain the bright soliton, dark soliton, gray soliton from these similarity equations with the numerical method. Furthermore, we investigate what factors contribute to the beamwidth of these solitons with the numerical method and know the beamwidth of these solitons are associated with the external electric field, the photovoltaic field and the intensity ratio of the incident soliton.     

C M ? C N D -computable state

The notions of D-computable state and D-concurrence are generalized to the C ^M ⊗ C ^N system. A class of D-computable state on C ^M ⊗ C ^N is given and the calculating method of the lower bound of D-concurrence is provided. The obvious expression of the lower bound of D-concurrence for the state mixed by two D-pure states is derived. Supported by the National Natural Science Foundation of China (Grant No. 60433050) and the Key Project of the Science Foundation of Xuzhou Normal University (Grant No. 06XLA05)     

Effect of an external electric field on two-dimensional nucleation

Summary Two-dimensional nuclei of different possible shapes are considered in the presence of an external electric field which is applied either perpendicular or parallel to the nucleation surface. The additional driving force needed for the formation of a nucleus due to the electric field is found and used in the nucleation theory. The results show that the electric field can either stimulate or inhibit the nucleation process depending on the ratio of the dielectric constants and the orientation of the applied electric field with respect to the nucleation surface. The dependence of the two-dimensional nucleation rate on the intensity of electric field is also determined.

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Riassunto Si considerano nuclei bidimensionali di differenti forme possibili in presenza di un campo elettrico esterno che è applicato sia perpendicolare che parallelo alla superficie di nucleazione. Si trova e si usa nella teoria di nucleazione l’ulteriore forza guida necesaria per la formazione di un nucleo a causa del campo elettrico. I risultati mostrano che il campo elettrico può sia stimolare che inibire il processo di nucleazione che dipende dal rapporto delle costanti dielettriche e dell’orientamento del campo elettrico applicato rispetto alla superficie di nucleazione. Si determina anche la dipendenza del valore di nucleazione bindimensionale dall’intensità del campo elettrico.

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Резюме Рассматриваются двумерные ядра различных возможиых форм в присутствии внешнего электрического поля, которое либо перпендикулярно, либо параллельно поверхности вародышеобразования. Определяется и используется в теории зародяшеобразования дополнительная движущая сила, необходимая для образования ядра, всл⪟дствие действия электрического поля. Полученные результатя показяают, что электрическое поле может либо стимулировать, либо тормозить процесс зародышеобразования в зависимости от отношения диэлектричеких постоянных и от ориентации приложенного электричеслог поля отнонительно поверхности зародышеодразования. Такзе определяется зависимость скорости образвания двумерных ядер от интенсивности электрического поля.

     

Surface spin-wave electrodynamics of an easy-axis antiferromagnet in an external electric field

The conditions are found under which quadratic magneto-optic interaction causes the formation of virtual surface magnetic TM and TE polaritons propagating along the interface between an antiferromagnet (AFM) and an ideal metal or between an AFM and an insulator in an external static electric field directed along the easy axis of the AFM. The specific features of the reflection of a bulk electromagnetic wave incident from vacuum onto the AFM surface are studied under these conditions.     

On the discharge in laser plasma in an external electric field

The possibility of creating discharge in laser plasma in an external electric field with quasi-static current generation along the field is discussed. The knowledge of the quasi-static current generation mechanism in laser plasma, associated with the rarefaction shock wave (RSW), allows the determination of the spatial distribution of these currents during laser irradiation of a planar target. Having included the (planar or cylindrical) target into an external contour, we propose a discharge scheme in laser plasma, where the discharge current increases during the laser pulse.     

Non-stationary holographic currents in BSO under an external sinusoidal electric field

We calculated the non-stationary holographic currents in an external sinusoidal electric field. We first solved numerically the set of nonlinear material rate differential equations to find the full overall space charged field and the mobile carrier density for a photorefractive BSO crystal. With these results we calculated the photocurrents and we obtained an additional term in the photocurrent when an ac field is applied. We have a good agreement between our theoretical and experimental data previously reported.