Effect of alkali metals on the surface energy of plutonium

The energy of plutonium at interfaces with melts of alkali metals is estimated using a modified version of the electron statistical method. The expressions for the polarization correction and temperature contribution are modified with allowance for changes in the electron density at the interface. The temperature dependence of the energy on the faces of plutonium modifications is calculated over a wide range of temperatures.     

Ab initio simulation of the electron structure and optical spectroscopy of ErRhGe compound

The results of investigation of the electronic structure and optical properties of ErRhGe are presented. The band spectrum of this compound is calculated in the local electron spin density approximation with correction for strong electron interactions in the 4f shell of the rare-earth metal (LSDA + U method) with allowance for the spin polarization. The optical constants of the compound are measured, and a number of spectral and electronic characteristics are determined by the ellipsometric method in a wide range of wave-lengths. Structural features of the optical conductivity spectrum in the interband absorption region are interpreted on the basis of the calculated electron state density.     

Core polarization and Coulomb displacement energies

A systematic study of the core polarization correction to Coulomb displacement energies is carried out. A zero range density independent and density dependent force is used to calculate this correction in the A = 16, A = 40, and A = 208 regions. It is found that the core polarization correction does not increase the Coulomb displacement energies and, therefore, cannot resolve the existing discrepancy between theory and experiment. Moreover, when the mean square radius of the excess neutron distribution is decreased the core polarization correction to the Coulomb energy becomes attractive and cancels the gain resulting from the direct Coulomb term. Hence, it is concluded that the discrepancy cannot be resolved even when the excess neutron distribution has an anomalously small radius. It is also pointed out that when the core polarization term is added the discrepancy is almost equal in mirror nuclei with a single hole in the N = Z core and those with a single particle outside the same core. Evidently, additional charge asymmetric corrections are required to resolve the discrepancies in Coulomb displacement energies.     

Test of electron screening and vacuum polarization in heavy muonic atoms

Energies of higherΜ X-rays have been measured in¹⁰³Rh,^natHg and²⁰³Tl to test the vacuum polarization correction and the electron screening effect in heavy muonic atoms. For tests of the energy calibration delayed nuclearγ-rays from theΜ-capture reaction were used. The experimental data agree to better than 4% with self-consistent Hartree-Fock calculations of the electron screening. Transitions which are sensitive to the vacuum polarization correction mainly, verify the calculations to better than 1.5%. Comparing all at present existing experiments with latest calculations no significant deviation of more than 0.7% of the vacuum polarization correction can be deduced.     

Electronic and Spectral Properties of RRhSn (R = Gd,Tb) Intermetallic Compounds

The investigations of electronic structure and optical properties of GdRhSn and TbRhSn were carried out. The calculations of band spectrum, taking into account the spin polarization, were performed in a local electron density approximation with a correction for strong correlation effects in 4f shell of rare earth metal (LSDA + U method). The optical studies were done by ellipsometry in a wide range of wavelengths, and the set of spectral and electronic characteristics was determined. It was shown that optical absorption in a region of interband transitions has a satisfactory explanation within a scope of calculations of density of electronic states carried out.     

Optical pumping of nuclear spin magnetization in GaAs/AlAs quantum wells of variable electron density

We report the use of time-resolved Faraday rotation to induce and probe the polarization of nuclear spins within a set of quantum wells with varying background electron density. The electron density was controlled over a broad range by making use of structures of mixed type-I/type-II GaAs/AlAs quantum wells that spatially separate photoexcited electron–hole pairs. We find that the optically detected nuclear magnetic field decreases quasi-monotonically with increasing electron density. The likely factors responsible for this behavior are increased electron spin-lattice relaxation, increased electron spin delocalization, and dilution of the electron spin polarization.     

Vertex correction of the anisotropic magnetic impurities to the spin polarization of 2D electron gas

In terms of Kubo's formula and Green's function method, for the two-dimensional electron gas (2DEG) with Rashba spin-orbit coupling (SOC), we study the spin polarization due to the effect from magnetic impurities with anisotropic spin dependent delta type coupling to electrons when an external dc electric field in plane is applied. The vertex correction of impurities in ladder approximation is carried out in the limit of EF?1/τ, Δ. We find that the strength of spin polarization can be significantly modified by vertex correction and the spin polarization is relevant to the anisotropy coefficient γ, but the direction of net spin polarization cannot be changed.     

Spherical electron-ion systems in semiclassical approximation: Atoms and atomic clusters

A semiclassical method for calculating the total energy and spatial distribution of electron density in spherically symmetric electron-ion systems is applied to atoms and both solid and hollow atomic clusters. Both exchange-correlation interaction and second-order gradient correction are taken into account. The contribution due to the fourth-order gradient correction is discussed. An expression is proposed for the oscillating correction to the averaged electron density. An expression is obtained for the equilibrium radius of a hollow cluster. The dependence of the equilibrium radius of an endohedral cluster on the valence of the central atom is analyzed.     

Radiation Emission of Fast Electrons in Collisions with “Ion‐Sphere” in Dense Plasmas

Radiative emission of fast electrons in collision with an “ion‐sphere” electron distribution in dense plasmas is under consideration. The electron structure of the ion sphere is calculated ab initio using self‐consistent solution of both bound and free electron distribution inside the sphere. Two radiation channels are included: emission of the colliding electron itself in static potential (conventional or static Bremsstrahlung) and the emission of “ion sphere” medium due to its polarization by the colliding electron (polarization Bremsstrahlung). The last one is calculated in the frame of local plasma density approximation. Interference between conventional and polarization Bremsstrahlung is taken into account. It is shown that spectral cross section of the process has characteristic features depending on plasma density and ionization stage of plasma ions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gate control of dynamic nuclear polarization in GaAs quantum wells

Gate control of dynamic nuclear polarization under optical orientation is demonstrated in a Schottky-gated n-GaAs/AlGaAs (110) quantum well by time-resolved Kerr rotation measurements. Spin relaxation of electrons due to mechanisms other than the hyperfine interaction is effectively suppressed as the donor induced background electron density is reduced from metallic to insulating regimes. Subsequent accumulation of photoexcited electron spins dramatically enhances dynamic nuclear polarization at low magnetic field, allowing us to tune nuclear spin polarization by external gate voltages.     

Magnetic phase diagram in a quasi-two-dimensional electron gas

Using spin density functional theory within the framework of the local spin density approximation with Perdew-Zunger type exchange-correlation energy, ferromagnetism in a quasi-two-dimensional electron gas (Q-2DEG) is studied. The electronic and magnetic structures of a thin film are calculated as a function of film thickness and electron density. Ferromagnetism in the Q-2DEG is found to appear at a higher electron density than in the three-dimensional electron gas. Unless a film is very thin, with decreasing electron density, a magnetic phase transition occurs from a spin-unpolarized fluid to a Wigner film with surface magnetism, in which the spin polarization localizes only in the neighborhood of surfaces. Further decreasing density induces another transition to a fully spin-polarized ferromagnetic Wigner film.     

Semiclassical model of a one-dimensional quantum dot

A one-dimensional quantum dot at zero temperature is used as an example for developing a consistent semiclassical method. The method can also be applied to systems of higher dimension that admit separation of variables. For electrons confined by a quartic potential, the Thomas-Fermi approximation is used to calculate the self-consistent potential, the electron density distribution, and the total energy as a function of the electron number and the effective electron charge representing the strength of interaction between electrons. Use is made of scaling with respect to the electron number. An energy quantization condition is derived. The oscillating part of the electron density and both gradient and shell corrections to the total electron energy are calculated by using the results based on the Thomas-Fermi model and analytical expressions derived in this study. The dependence of the shell correction on the interaction strength is examined. Comparisons with results calculated by the density functional method are presented. The relationship between the results obtained and the Strutinsky correction is discussed.     

类锂体系激发态1s2 nd(n=3,4,5)精细结构和项能的理论计算

使用全实加关联(fullcorepluscorrelation缩写为FCPC)和里兹(Ritz)变分方法计算了类锂体系(Z=11—20)激发态1s2nd(n=3,4,5)的非相对论能量和波函数;包括动能修正、电子电子接触项、轨道轨道相互作用项以及Darwin项的相对论修正和质量极化项由全实加关联波函数的一阶微扰给出,量子电动力学(quantumelectronicdynamics缩写为QED)修正由有效核电荷方法和类氢公式计算;给出了高电离类锂体系激发态的激发能、精细结构和项能(termenergy),并 关键词： 类锂体系 全实加关联 精细结构 激发能     

Ferromagnetism of Electron Gas

We here investigate the density and temperature dependence of polarization using the relativistic formalism for the electron–electron interaction within the Fermi liquid model. The variational method has been used: the free energy has been minimized with respect to the effective mass and the polarization parameter. Then we obtained the equation of state and magnetic susceptibility of the system. The exact results for polarization and magnetic susceptibility have been obtained at zero temperature. It has been shown that for a given temperature (density) there is a critical density (temperature) at which the ferromagnetic phase can appear in an electron gas. The results are in agreement with previous work. Our results show that at nonzero temperatures and in very low and very high densities the ferromagnetism phase cannot exist.     

Spin-dependent current in resonant tunneling diode with ferromagnetic GaMnN layers

The spin-polarized tunneling current through a double barrier resonant tunneling diode (RTD) with ferromagnetic GaMnN emitter/collector is investigated theoretically. Two distinct spin splitting peaks can be observed at current-voltage (I-V) characteristics at low temperature. The spin polarization decreases with the temperature due to the thermal effect of electron density of states. When charge polarization effect is considered at the heterostructure, the spin polarization is enhanced significantly. A highly spin-polarized current can be obtained depending on the polarization charge density.     

Inhomogeneous polarizable medium as a model for an electron gas in a nonconducting crystal

The response of the electron system to an external perturbation in an insulating medium is considered in the context of the electron density functional method. The energy functional minimization relies on the proper choice of the trial function considering different spatial scales of the electron polarization. An efficient scheme for the density functional parametrization is suggested. The electron response to atomic displacements and external electric fields has been calculated for a simple model of electron polarization centers embedded into the homogeneous dielectric background. Good agreement with the experiment is achieved for the phonon spectra ofSi, Ge, and α-Sn. The electron density induced in the external homogeneous electric field is in good agreement with that calculated by the well-known ab initio methods. V. D. Kuznetsov Siberian Physical-Technical Institute at Tomsk State University. Translated for Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6 pp. 30–37, June, 1999.     

Effect of spontaneous and piezoelectric polarization on optical characteristics of ultraviolet AlGaInN light-emitting diodes

Polarization is a crucial issue for electrical and optical characteristics of the UV AlGaInN light-emitting diodes. The effect of spontaneous and piezoelectric polarization on optical characteristics of the UV AlGaInN light-emitting diodes is investigated numerically. The simulation results indicate that the polarization-related effect for the UV AlGaInN light-emitting diodes is dominated by the piezoelectric polarization. When the UV AlGaInN light-emitting diodes are without piezoelectric polarization, the optical performance is enhanced effectively due to improved overlap of electron and hole wavefunctions, reduced electron leakage current, and increased density of holes in the active region.     

Effect of polarization roughness scattering (PRS) on two-dimensional electron transport of MgZnO/ZnO heterostructures

Quantum transport properties of two-dimensional electron gas (2DEG) in undoped MgZnO/ZnO heterostructures with polarization charge effect have been investigated theoretically. Polarization roughness scattering (PRS) combining polarization charge and interface roughness scattering was proposed as a new scattering mechanism. It was found that the carriers confined in the heterostructures (HSs) would be scattered from polarization charges when they were moving along the in-plane and PRS played a very important role for the low-temperature electron mobility when the electron density N_s exceeded 1.0e11 cm⁻², especially in a higher electron density region. With PRS, the experimental data on the density dependence of 2DEG mobility in the MgZnO/ZnO HSs under study can be well reproduced. The study indicates that the improved processing techniques providing a smooth interface and a good separation between the 2DEG electrons and the polarization charges should be significant for the quantum device’s performance.     

Two-photon-exchange correction to parity-violating elastic electron-proton scattering

Higher-order QED effects play an important role in precision measurements of nucleon elastic form factors in electron scattering. Here we introduce a two-photon-exchange QED correction to the parity-violating polarization asymmetry of elastic electron-proton scattering. We calculate this correction in the parton model using the formalism of generalized parton distributions, and demonstrate that it can reach several percent in certain kinematics, becoming comparable in size with existing experimental measurements of strange-quark effects in the proton neutral weak current.