Bandgap Narrowing in Quantum Wires

In this paper we consider two different geometry of quasi one-dimensional semiconductors and calculate their exchange-correlation induced bandgap renormalization (BGR) as a function of the electron-hole plasma density and quantum wire width. Based on different fabrication scheme, we define suitable external confinement potential and then leading-order GW dynamical screening approximation is used in the calculation by treating electron-electron Coulomb interaction and electron-optical phonon interaction. Using a numerical scheme, screened Coulomb potential, probability of different states, profile of charge density and the values of the renormalized gap energy are calculated and the effects of variation of confinement potential width and temperature are studied.Comment: 17 Pages, 4 Figure

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

Хлорфенолы в органическом синтезе

Received: 17.08.2016; accepted: 11.10.2016; published: 01.12.2016.Поступило: 17.08.2016; приянято: 11.10.2016; опубликовано: 01.12.2016.This article reviews the alternatives for modifications of p-chlorophenols, p-chloroanisoles with the formation of C-C, C-N, C-S and C-B bonds. It is worth noting the high fundamental as well as practical importance of these reactions due to the availability and cheapness of initial chlorine substituted derivatives of phenol.В данном обзоре рассмотрены варианты модификаций п-хлорфенолов и п-хлоранизолов с образованием связей C-C, C-N, C-S и C-B. Стоит отметить высокую не только фундаментальную, но и практическую значимость данных реакций, ввиду доступности и дешевизны исходных хлорзамещенных производных фенола

Toward the creation of terahertz graphene injection laser

We study the effect of population inversion associated with the electron and hole injection in graphene p-i-n structures at the room and slightly lower temperatures. It is assumed that the recombination and energy relaxation of electrons and holes is associated primarily with the interband and intraband processes assisted by optical phonons. The dependences of the electron-hole and optical phonon effective temperatures on the applied voltage, the current-voltage characteristics, and the frequency-dependent dynamic conductivity are calculated. In particular, we demonstrate that at low and moderate voltages the injection can lead to a pronounced cooling of the electron-hole plasma in the device i-section to the temperatures below the lattice temperature. However at higher voltages, the voltage dependences can be ambiguous exhibiting the S-shape. It is shown that the frequency-dependent dynamic conductivity can be negative in the terahertz range of freqiencies at certain values of the applied voltage. The electron-hole plasma cooling substantially reinforces the effect of negative dynamic conductivity and promotes the realization of terahertz lasing. On the other hand, the heating of optical phonon system can also be crucial affecting the realization of negative dynamic conductivity and terahertz lasing at the room temperatures.Comment: 10 pages, 7 figure

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

Хлорфенолы в органическом синтезе

This article reviews the alternatives for modifications of p-chlorophenols, p-chloroanisoles with the formation of C-C, C-N, C-S and C-B bonds. It is worth noting the high fundamental as well as practical importance of these reactions due to the availability and cheapness of initial chlorine substituted derivatives of phenol.В данном обзоре рассмотрены варианты модификаций п-хлорфенолов и п-хлоранизолов с образованием связей C-C, C-N, C-S и C-B. Стоит отметить высокую не только фундаментальную, но и практическую значимость данных реакций, ввиду доступности и дешевизны исходных хлорзамещенных производных фенола