Inhomogeneous broadening of intersubband transitions due to nonscreening roughness of heterointerfaces

The shape of the terahertz absorption peak in quantum wells with rough heterointerfaces is studied. Although the long-range variations of the ground level are screened in heavily doped structures, the intersubband in-plane energy remains nonuniform due to the second-level variations. The equation for intersubband polarization is considered in the resonant approximation, taking into account the depolarization shift. The line shape of the intersubband absorption peak is described for the case with long-range variations of heterointerfaces. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70071/2/JAPIAU-87-7-3582-1.pd

Ground-state properties of the one-dimensional electron liquid

We present calculations of the energy, pair-correlation function (PCF), static structure factor (SSF), and momentum density (MD) for the one-dimensional electron gas using the quantum Monte Carlo method. We are able to resolve peaks in the SSF at even-integer multiples of the Fermi wave vector, which grow as the coupling is increased. Our MD results show an increase in the effective Fermi wave vector as the interaction strength is raised in the paramagnetic harmonic wire; this appears to be a result of the vanishing difference between the wave functions of the paramagnetic and ferromagnetic systems. We have extracted the Luttinger liquid exponent from our MDs by fitting to data around kF, finding good agreement between the exponent of the ferromagnetic infinitely thin wire and the ferromagnetic harmonic wire

Magnetoresistance of a semiconducting magnetic wire with domain wall

We investigate theoretically the influence of the spin-orbit interaction of Rashba type on the magnetoresistance of a semiconducting ferromagnetic nanostructure with a laterally constrained domain wall. The domain wall is assumed sharp (on the scale of the Fermi wave length of the charge carriers). It is shown that the magnetoresistance in such a case can be considerably large, which is in a qualitative agreement with recent experimental observations. It is also shown that spin-orbit interaction may result in an increase of the magnetoresistance. The role of localization corrections is also briefly discussed.Comment: 5 pages, 2 figure

Electronic states in heterostructures formed by ultranarrow layers

Low-energy electronic states in heterosrtuctures formed by ultranarrow layer (single or several monolayers thickness) are studied theoretically. The host material is described within the effective mass approximation and effect of ultranarrow layers is taken into account within the framework of the transfer matrix approach. Using the current conservation requirement and the inversion symmetry of ultranarrow layer, the transfer matrix is written through two phenomenological parameters. The binding energy of localized state, the reflection (transmission) coefficient for the single ultranarrow layer case, and the energy spectrum of superlattice are determined by these parameters. Spectral dependency of absorption in superlattice due to photoexcitation of electrons from localized states into minibands is strongly dependent on the ultranarrow layers characteristics. Such a dependency can be used for verification of the transfer matrix parameters.Comment: 7 pages, 7 figure

Superlattice formed by quantum-dot sheets: density of states and IR absorption

Low-energy continuous states of electron in heterosrtucture with periodically placed quantum-dot sheets are studied theoretically. The Green's function of electron is governed by the Dyson equation with the self-energy function which is determined the boundary conditions at quantum-dot sheets with weak damping in low-energy region. The parameters of superlattice formed by quantum-dot sheets are determined using of the short-range model of quantum dot. The density of states and spectral dependencies of the anisotropic absorption coefficient under mid-IR transitions from doped quantum dots into miniband states of superlattice strongly depend on dot concentration and on period of sheets. These dependencies can be used for characterization of the multi-layer structure and they determine parameters of different optoelectronic devices exploiting vertical transport of carriers through quantum-dot sheets.Comment: 7 pages and 5 figure

A clinical case of restoration of the destroyed crown part of the tooth complicated by changes in the bifurcation area

The destruction of the tooth crown should be regarded as the cause leading over time to the disruption of the morphofunctional unity of the dentition and pathological condition of the entire dentoalveolar system. Untimely treatment of defects of hard tooth tissues leads to functional disorganization of the dentoalveolar system. The most eliminated defects are those of crowns of teeth determining the quality of aesthetics, phonetics, functions of biting and chewing. The destruction of the tooth crowns, which do not cause significant disruption of the above functions, are painless and almost asymptomatic. In such cases, deformation of the dentition and occlusion, dysfunction of masticatory muscles and temporomandibular joints as well as the development of pathological changes in periodontium occur slowly. Of great importance are the early diagnosis of pathological reconstruction of dentoalveolar system and the knowledge of pathogenesis of possible complications after the extraction of the teeth that determine the indications for prophylactic orthopedic dental treatment. The article presents a clinical case of restoration of destructed tooth crown 3.6 complicated by changes in bifurcation area. The patient underwent coronary-radicular separation with the use of cast metal cores, which allowed restoration of the sufficient size of the stump, function and anatomical shape of the tooth and hence the unity of dental arch