Modification of the rabi flopping frequency in the presence of a static electric field

For a two-level system the net probability for stimulated one-photon emission in the presence of a static electric field is calculated within the rotating-wave approximation and under the assumption that the static field strength (E^S) is considerably less than the oscillating field strength (E^O). Besides contributing to the power broadening of the emission signal and the Rabi flopping frequency, the static field shifts the resonance towards the blue in the amount 2E^S/E^O.     

Photodetachment of H- in a static electric field

We derive a formula using closed-orbit theory for the photodetachment cross-section of H^- in the presence of a static electric field when there is an arbitrary angle θ_L between the laser polarization direction and the static electric field. This formula generalizes the previous result for laser polarization parallel to the static electric field, the effect of laser polarization direction appears as a factor cos²(θ_L) in the amplitude of the oscillation. A photodetachment cross-section formula valid above and below detachment threshold is proposed.     

Investigations on the soft-mode mechanism of the ferroelectric phase transition in

Dielectric and Raman spectroscopic measurements have been performed to investigate the ferroelectric phase transition in . Single crystals were grown by the zone melting method. The frequency dependence of the dielectric permittivity from 1 MHz to 1 GHz has been studied in a temperature range between 265 and 285 K. A Debye like dielectric dispersion was found, showing a critical slowing down around K. Polarized Raman spectra have been taken between 220 and 310 K. Two softening modes have been found, one of A- and another one of B / B g-symmetry. The phase transition mechanism in can be classified as partially order-disorder and partially displacive, confirming former structural results. It resembles strongly that of monoclinic . Received: 7 April 1998 / Revised: 5 June 1998 / Accepted: 16 June 1998     

Deformation of a ferroelectric smectic film in an electric field

Mechanisms of static deformation of a freely suspended ferroelectric smectic (C*) film in an external transverse electric field are analyzed. An equation for the shape of the film that includes the interaction of the applied field with the polarization vector and surface charges is derived in terms of the variational approach. The effect of deformation is shown to be of threshold character, which agrees with the experimental data.     

Reversible polarization of ferroelectric ceramics in a rapid-growing electric field

The complex permittivity of ferroelectric PZT ceramics with different compositions was measured in a pulsed rapid-growing electric field. The time dependence of the real component exhibits three peaks. The dips between them correlate with imaginary component peaks. Domain mechanisms that contribute to the ferroelectric polarization and are responsible for the time dependences are considered.     

Durability of polycrystalline ferroelectric ceramics in a constant electric field

The kinetics of mechanical fracture and electric breakdown of polycrystalline ferroelectric ceramics under simultaneous action of an electric field and mechanical load have been investigated. The procedures for determining the activation characteristics of both processes from only the fracture kinetics in one of them have been developed.     

三维静电场实验仪

为克服传统方法不能真实反映静电场的三维本质,综合应用了机械、电子、MCU、传感器、步进电机和计算机接口等技术研制了静电场三维实验仪,实现了静电场的三维空间坐标量和电量的测控,并用所研制的静电场三维实验仪对部分特殊电极所形成的电场进行了模拟实验研究.     

Behavior of semiconductors in an SHF electric field

Conclusions These experimental results have shown that when an shf electric field is applied to a small semiconducting sample there is a redistribution of free carriers in the sample, which results in an increase in the carrier concentration near the sample boundaries and a decrease in the center. Carrier trapping at the sample surface has a pronounced effect on this redistribution.Since the carrier redistribution and trapping at the surface may significantly affect the characteristics of several practical devices in which small semiconducting samples are used, it is worthwhile to pursue the theoretical and experimental study of this behavior.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 7–11, October, 1970.     

Highly excited atomic states in a static electric field

We have performed exact numerical calculations for a hydrogen atom perturbed by a uniform electric field for some Stark sublevels with n = 12, 13, 14, 15. The results are compared with recent experimental data for excited states of sodium.     

Electrocaloric response of a ferroelectric capacitor to a periodic electric field

The electrocaloric response of a ferroelectric capacitor to a periodic electric field has been analyzed in terms of the nonstationary heat conduction equation. A linear physical model is considered for an electrocaloric element in which one end (x = 0) is thermally insulated and a constant temperature T ₀ is maintained at the boundary x = l. The effect of a periodic electric field on the capacitor gives rise to temperature oscillations about a decreasing average value that reaches saturation. A relatively simple analytic expression is derived for the temperature distribution along the electrocaloric element and the heat flux density under stationary conditions. The calculations are carried out using the results obtained from measurements performed for a PMN-PT relaxor ferroelectric in the temperature range of the phase transition. A temperature gradient and a heat flux of ～150 W/cm² are observed in an electric field of 2.4 V/μm at a frequency of 10 Hz.     

On the hopping conduction mechanism of amorphous semiconductors in a strong electric field

The theory of the hopping conduction by the radiative tunnel transitions (RTT) in a strong electric field is applied to amorphous silicon and germanium. On the basis of numerical estimations we suggest that the relative contribution of the RTT mechanism into the total strong electric field hopping conductivity of an amorphous semiconductor could be significant.     

Bulk superconductor in weakly static electric field

We investigate the properties of bulk superconductors in weakly static electric fields by a stationary perturbation method applied to the Schrödinger equation.     

Optical anisotropy of zinc-blende semiconductors in an electric field

A theory of optical anisotropy for zinc-blende semiconductors in an electric field is derived by extending the formalism of Luttinger and Kohn [Phys. Rev. 97, 869 (1955)] to higher order. This resolves a recent controversy over the correct form of the Hamiltonian for the degenerate valence bands.     

Two-photon interband transitions in semiconductors in a static magnetic field. Nonlocal effects

Summary It is shown that in the presence of a static magnetic field, the electronic states in the effective-mass approximation are described by a Hamiltonian containing a nonlocal potential. In order to preserve the gauge invariance of the transition rates, the interaction between the electrons and the radiation has to be modified. For ZnS, the transition rate between two particular levels is evaluated by showing a difference of more than one order of magnitude when compared with the transition rate previously calculated. Partially supported by the Italian Research Council (C.N.R.) through G.N.S.M.     

Behavior of a lead scandium tantalate ferroelectric in an ac electric field

The behavior of an incompletely ordered lead scandium tantalate ferroelectric (the degree of ordering s=0.8) in the region of the spontaneous ferroelectric transition is studied in ac electric fields by dielectric and optical methods. Dielectric nonlinearity of two types is observed. In fields above 2 kV/cm, the nonlinearity is caused by induced polarization effects and macrohysteresis behavior, whereas in weak fields, it is most probably associated with the dynamics of domain walls and/or phase boundaries.     

Nonuniform electric field effects on zener tunneling in semiconductors

Expressions for Zener tunneling probability, which are based on a simple two-band theory and a nonuniform electric-field of the profile ε = ε₀e^?ax, are calculated explicitly. It is shown that the magnitude of tunneling probability increases as the penetration depth of the electric field decreases. Also numerical example for InSb is discussed.