Influence of electric field,hydrostatic pressure and temperature on the electronic states in a Pöschl-Teller quantum well

Influence of the electric field and hydrostatic pressure on the electronic states in a Pöschl-Teller quantum well is studied. In the framework of variational method the dependences of the ground state energy on the electric field and hydrostatic pressure are calculated for different values of the potential parameters and the temperature. It is shown that the increase in the electric field leads to the increase in the ground state energy, while the increase in the well width leads to the strengthening of the electric field effect. The ground state energy decreases with increasing pressure and increases with increasing temperature.     

Binding energy and photoionizaiton cross-section of hydrogen-like impurity in a Pöschl-Teller quantum well

The effect of the donor impurity position and the form of confining potential on the binding energy and the photoionization cross-section in a semiconductor quantum well with the Pöschl-Teller potential is studied. An analytical expression for the photoionization cross-section is obtained for the case when the polarization vector of light wave is directed along the direction of size quantization. It is shown that the photoionization cross-section has a threshold behavior.     

Nonlocal effects on second-harmonic generation in a Pöschl-Teller quantum well

Nonlocal effects on the energy conversion efficiency of the second-harmonic generation (SHG) for a p-polarized incident field in a P?schl-Teller quantum well (PTQW) are investigated in detail. The numerical results show that the spatial distribution of the second-harmonic field is nonuniform, and that there exist two resonance peaks in the second-harmonic energy reflection spectra, and their positions have a notable blueshift because of the nonlocal effects. A very important property is that a maximum blueshift at the second-harmonic resonance can be obtained by adopting a proper quantum-well width and donor concentration, which may be interesting in future precision experiments.     

Electric field effect on the binding energy of a hydrogenic impurity in coaxial GaAs/Al xGa1 − x As quantum well-wires

The ground state binding energy of a hydrogenic impurity in a coaxial cylindirical quantum well wire system subjected to an external electric field applied perpendicular to the symmetry axis of the wire system is studied within a variational scheme. Binding energy calculations were performed as functions of the inner barrier thickness and the electric field for two different impurity positions. The main result is that a sharp decrease in the binding energy, which may be important in device applications, occurs in certain conditions.     

Schrödinger equation for a particle on a curved surface in an electric and magnetic field

We derive the Schr?dinger equation for a spinless charged particle constrained to move on a curved surface in the presence of an electric and magnetic field. The particle is confined on the surface using a thin-layer procedure, which gives rise to the well-known geometric potential. The electric and magnetic fields are included via the four potential. We find that there is no coupling between the fields and the surface curvature and that, with a proper choice of the gauge, the surface and transverse dynamics are exactly separable. Finally, we derive an analytic form of the Hamiltonian for spherical, cylindrical, and toroidal surfaces.     

Effect of electric field on the spectrum and the persistent current of a quantum ring with two electrons （II） additional effect of a charged impurity

This paper studies the effect of a charged impurity together with or without an external homogeneous electric field on a quantum ring threaded by a magnetic field B and containing two electrons. The potential caused by the impurity has been plotted which is helpful to the understanding of the electronic structures inside the ring. The deep valley appearing in the potential curve is the source of localization, which affects seriously the Aharonov-Bohm oscillation （ABO） of the energy and persistent current. It also causes the fluctuation of the total orbital angular momentum L of the pair of electrons. It is found that the appearance of the impurity reduces the domain of the fractional ABO. During the increase of B, the domain of the integral ABO may appear earlier when B is even quite small. The transition from the localized states to extended states has also been studied. Furthermore, it has deduced a set of related formulae for a transformation, by which an impurity with a charge ep placed at an arbitrary point Rp is equivalent to an impurity with a revised charge ep placed at the X-axis with a revised radial distance Rp. This transformation facilitates the calculation and make the analysis of the physical result clearer.     

Electronic states in a cylindrical quantum dot with the modified Pöschl-Teller potential in the presence of external magnetic field

Energy levels of an electron in a cylindrical quantum dot with a modified Pöschl-Teller potential in the presence of external homogeneous magnetic field are studied. Analytical expressions for the wave function and energy of the particle are obtained. Different regimes of magnetic quantization are considered and peculiarities of behavior of the electron energy spectrum depending on the value of applied magnetic field are revealed.     

Effects of Rashba spin–orbit coupling and a magnetic field on a polygonal quantum ring

Using standard quantum network method, we analytically investigate the effect of Rashba spin–orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer–Büttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain.     

Effects of an anisotropic parabolic potential and Coulomb’s impurity potential on the energy characteristics of asymmetrical semi-exponential CsI quantum wells

Because of its unique optoelectronic properties,people have studied the characteristics of polarons in various quantum well(QW)models.Among them,the asymmetrical semiexponential QW(ASEQW)is a new model for studying the structure of QWs in recent years.It is of great significance to study the influences of the impurity and anisotropic parabolic confinement potential(APCP)on the crystal’s properties,because some of the impurities,usually regarded as Coulomb’s impurity potential(CIP),will exist in the crystal more or less,and the APCP has flexible adjustment parameters.However,the energy characteristics of the ASEQW under the combined actions of impurities and APCP have not been studied,which is the motivation of this paper.Using the linear combination operation and Lee-Low-Pines unitary transformation methods,we investigate the vibrational frequency and the ground state energy of the strong coupling polaron in an ASEQW with the influences of the CIP at the origin of coordinates and APCP,and make a comparison between our results and previous literature’s.Our numerical results about the energy properties in the ASEQW influenced by the CIP and APCP may have important significances for experimental design and device preparation.     

Kinetics of the magnetization reversal in permalloy–niobium microstrips under the effect of a pulsed magnetic field and an electric current

The kinetics of magnetization reversal in bilayer permalloy–niobium microstrips under the effect of both a pulsed magnetic field and an electric current has been experimentally studied. These two cases turn out to be fundamentally different in the types of arising magnetic structures and in the dynamic characteristics of the processes. Such difference is especially striking at low temperatures. An anomalously high rate of the processes under study is observed. According to the suggested qualitative explanation, this effect is due to nonlinear excitations appearing in front of the moving domain wall if the applied electric current lowers the barriers for its motion. For achieving the final conclusions, more accurate quantitative analysis is needed.     

The energy–momentum distributions and relativistic quantum effects on scalar and spin-half particles in a Gödel-type space–time

In this article, the energy–momentum distributions associated with a topologically trivial Gödel-type space–time, using different complexes of Møller, Einstein, Landau–Lifshitz, Papapetrou, and Bergmann–Thomson, is evaluated. The results obtained here may support the Cooperstock’s energy localization hypothesis. Finally, we investigate the relativistic quantum effects on scalar and spin-half particles in this space–time without any potential, and analyse the influence of vorticity parameter on the energy eigenvalues of the system.     

Focusing effect and modulation mechanism of the beam self-fields on the electronʼs Larmor rotation in a free-electron laser with an axial guide magnetic field

It is revealed that at anti-resonance in a free-electron laser with a reversed guide magnetic field, the beam self-fields can act to focus the beam transport and prevent the electrons from striking on the waveguide wall before the wiggler exit. It is found that the focusing function results from the modulation of the periodically-varying self-field tangential and normal components on the electron?s Larmor rotation. As a potential application, substantial improvement of the wave gain and output power at anti-resonance could be expected, since the beam current loss can be obviated by using this modulation mechanism.     

The effects of electric and magnetic fields on the current spin polarization and magnetoresistance in a ferromagnetic/organic semiconductor/ferromagnetic（FM/OSC/FM） system

From experimental results of spin polarized injection and transport in organic semiconductors(OSCs),we theoretically study the current spin polarization and magnetoresistance under an electric and a magnetic field in a ferromagnetic/organic semiconductor/ferromagnetic(FM/OSC/FM) sandwich structure according to the spin drift-diffusion theory and Ohm’s law.From the calculations,it is found that the interfacial current spin polarization is enhanced by several orders of magnitude through tuning the magnetic and electric fields by taking into account the specific characteristics of OSC.Furthermore,the effects of the electric and magnetic fields on the magnetoresistance are also discussed in the sandwich structure.     

Comment on “On the threshold characteristics of the flexoelectric domains arising in a homogeneous electric field: The case of anisotropic elasticity” by Y.G. Marinov and H.P. Hinov

It is demonstrated that the key findings of the paper by Y.G. Marinov and H.P. Hinov, Eur. Phys. J. E 31, 179–189 (2010), are in direct conflict with the general physical background of flexoelectric domains. This is caused by a methodological error in the theoretical analysis of the paper.