The propagator of conduction electrons in semiconductors with a delta-barrier or a delta-well potential I. General

The one-dimensional propagator problem is solved for conduction electrons near a planar defect imitated by a delta-barrier or by a delta-well in a semiconductor. On condition that interband transitions may be neglected, the propagator is derived for a wide class of (possibly non-parabolic) functions fitting in with the dispersion function E(k) in the bottom part of the conduction band.     

The spin polarization of conduction electrons in ferromagnetic semiconductors

Within the framework of the s?f exchange model the exact asymptotics of the spin polarization of conduction electrons in the non-degenerate ferromagnetic semiconductor at low temperatures is calculated. It is demonstrated that the temperature dependent corrections to the total density of states are proportional to $\text{T}{}^{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$.     

Exact propagator for an electron in a quadratic saddle-point potential and a magnetic field

We study the propagator for an electron moving in a two-dimensional (2D) quadratic saddle-point potential,in the presence of a perpendicular uniform magnetic field. A closed-form expression for the propagator is derived using the Feynmann path integrals.     

Interaction of conduction electrons with local excitations. The infrared divergencies

Using the renormalization group method the higher orders of perturbation theory in the interaction of conduction electrons in metals with local paulions (pseudospins), e.g. two-level systems, crystal-field excitations, and bosons, e.g. phonons, are considered. For the paulions, the lowest order logarithmic singularities in the electron self-energy at =E–E _F±, being the splitting, become weaker, at least in the commutative model. It is shown that the singularities of the type ln are absent. This justifies the applicability of the second order perturbation theory resultm ^{* –1} for the electron effective mass even atm ^*m. For the phonons, the singularities at ±₀, ₀ being the phonon frequency, may become stronger or weaker depending on the conduction band filling and the anharmonic contribution to the deformation potential. The singular contributions to the local excitation Green's function are calculated. They result in the change of the line shape of the local level (the orthogonality catastrophe). The singular terms in the ground state energy and average pseudospin are considered.     

Transport and heating of electrons in semiconductors with a one-dimensional superlattice

On the basis of the Boltzmann equation with a new model collision integral that takes into account the redistribution of energy and momentum of all degrees of freedom of the electron, we have constructed and investigated a three-dimensional model of electron transport in one-dimensional semiconductor superlattices (SL’s). The current-voltage curves (CVC), mean energies, and effective temperatures of the electrons have been found for vertical and longitudinal transport. In contrast to one-dimensional models, the approach developed here allows one to take into account and describe not only longitudinal electron heating, but also electron heating transverse to the current. For vertical transport, transverse heating substantially alters the position, magnitude, and width of the current maximum. For longitudinal transport, electron heating that is non-quadratic in the field arises along the superlattice axis even in the approximation of a linear current-voltage characteristic. The possibility of describing electron transport in a superlattice using a mixed Fermi distribution with an isotropic temperature is analyzed. Fiz. Tverd. Tela (St. Petersburg) 41, 1698–1706 (September 1999)     

The propagator for a time-dependent mass subject to a harmonic potential with a time-dependent frequency

We find the quantum propagator of the harmonic oscillator with a time-dependent mass solving directly the Schrödinger equation through a change of variable and a time reparametrization.     

Cyclotron resonance study of conduction electrons in n-type indium antimonide under a strong magnetic field—II: Hot electrons

A system of hot electrons in the n-InSb under the application of a strong magnetic field has been studied by far IR cyclotron resonance. A three band model and an energy independent scattering time were assumed in analyzing the line shape variation with electric field applied either parallel or perpendicular to the magnetic field. Two kinds of electron temperature, inter- and intra-subband, were introduced to describe the electron distribution in energy space. The electron distribution function was found to deviate from an essentially Maxwellian form in the manner predicted by Yamada and Kurosawa. A remarkable difference exists between the two geometries: E∥H and E⊥U. A brief survey of cyclotron emission, and the reverse process of hot electron cyclotron absorption, is summarized at the end as an addendum.     

The contact charge density of conduction electrons of Fe in Co metal as derived from internal conversion

From an internal-conversion measurement of the 14.4 keV transition ⁵⁷Fe, the contact 1 charge density of conduction electrons for Fe in Co metal was obtained to be ?_4s(0) = 4.6 ±0.4 a₀⁻³, which is close to theoretical values but is smaller than that for Fe in Fe metal obtained recently.     

Spin density distribution of the conduction electrons in diperylene hexafluorophosphate analysed by high-resolution NMR

High-resolution ¹³C nuclear magnetic resonance with ¹H cross polarization and ¹H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate (including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed. From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack. The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals. Received 29 June 1999 and Received in final form 4 November 1999     

Interaction of conduction electrons in solids

It is shown that the influence of the interaction of conduction electrons with phonons can be partly included in the potential energy of their interaction. The effective potential energy found is used to study the possibility of the existence of bound states of two electrons in polar, homopolar and metallic crystals.     

A.c. hopping conduction in Mn-Co-Ni-Cu complex oxide semiconductors with spinel structure

The radio-frequency (RF) conductivities of spinel-type Mn-Co-Ni-Cu complex oxide semiconductors were investigated at low temperatures for ceramic samples with various Cu contents. The a.c. conductivities show large frequency dependences, which are ascribed to hopping of localized carriers between Mn ions at oxygen octahedral sites. When the Cu content is increased, the conductivity increases markedly and its frequency dependence is weakened. The hopping is considered to be a random walk process because the hopping sites are randomly distributed at the spinel oxygen octahedral sites. In this situation, the random walk theory in disordered systems developed by Scher and Lax is applicable, and the experimental results agree with this theory very well. The reduced frequency dependence is also successfully explained in this way. The Cu ions in these complex oxides lead to an increase in the localized carrier transition probability, and consequently lead to an increase in conductivity and a reduction in the frequency dependence of the a.c. conductivity.     

飞秒强激光作用下线性等离子体层中光场和电子密度的自洽分布

自洽求解了圆偏振的飞秒强激光作用下线性等离子体层中光场和电子密度的分布.研究发现在激光有质动力的作用下，电子密度分布严重偏离离子密度分布，甚至出现了一系列的“电子岛”和“电子空腔”.由于电荷分离，等离子体内形成了很强的静电场，一部分激光能量转化为等离子体内的静电能.线性等离子体层储存静电能的大小随着入射激光强度的增加而显著上升. 关键词： 飞秒激光 相对论等离子体 电子密度 有质动力     

Envelope equation for a relativistic electron beam with a self-similar current density profile propagating in a dense or rarefied gas-plasma medium along an applied magnetic field

An equation for the envelope of an azimuthally symmetric relativistic electron beam with an arbitrary self-similar profile is derived. It includes the nonlaminarity of the beam and its scattering by the residual gas, as well as the presence of a longitudinal magnetic field and a focusing radial electric field produced by the ionic background.