Electron Spin Alignment in InSb Type‐II Quantum Dots in an InAs Matrix
Electronic spin polarization up to 100 % has been observed in type‐II narrow‐gap heterostructures with InSb quantum dots in an InAs matrix via investigation of circular‐polarized photoluminescence at external magnetic field applied in Faraday geometry. Energy spectrum of holes confined in monolayer scale InSb/InAs quantum well is calculated using tight‐binding approach. The observed effect is explained in terms of strong Zeeman splitting of electrons in InAs matrix due to their large intrinsic g‐factor and corresponding optical transition selection rules. Temperature dependence of polarization degree well fit obtained data providing its experimental verification of suggested model.
We present a theoretical analysis of the split-off states emerging due to a tunnel coupling between a remote bound state and a semiconductor quantum well (QW). The on-site Coulomb repulsion and the spin splitting of the bound state have been considered. The split-off states emerge in the band gap of the QW and reveal themselves as two solitary peaks in the photoluminescence (PL) from the QW. The peaks have opposite circular polarization and their spectral position strongly depends on the tunnel coupling strength. We suggest a mechanism of ultrafast PL polarization switching by means of electrical modulation of the tunnel coupling by an external gate. The obtained results open a new possibility for the spin and optical polarization control in nanoscale systems.
Multiple Mn2+ spin-flip Raman scattering (SFRS) in Voigt geometry was observed in self-organized disk-shaped quantum dots (QDs) of CdSe/Zn0.99Mn0.01Se, where magnetic ions and QD carriers are spatially separated and therefore the exchange interaction between them is expected to be weak. Many lines (about ten) were observed in SFRS spectra, yet the overlapping of the hole wave function with Mn2+ ions is very small, in agreement with both the absence of observable Zeeman splitting of the photoluminescence line and the calculation. Interesting polarization properties of SFRS spectra were observed which could be affected by tilting the sample out of normal alignment and changing the temperature. These polarization properties were attributed to the selection rules in SFRS in Voigt geometry. It has been found that the theoretical model suggested by Stühler et al. [J. Cryst. Growth 159, 1001 (1996)] does not describe the SFRS spectra in systems with weak exchange interaction between charge carriers and magnetic ions. A qualitative model is suggested here for description of SFRS in such systems.
We have analyzed theoretically quenched dynamics of correlated double quantum dot (DQD) due to the switching “on” and “off” coupling to reservoirs. The possibility for controllable manipulation of charge and spin states in the double quantum dot was revealed and discussed. The proposed experimental scheme allows to prepare in DQD maximally entangled pure triplet state and to drive it to another entangled singlet state by tuning both applied bias and gate voltage. It was also demonstrated that the symmetry properties of the total system (double quantum dot coupled to electron reservoirs) allow to resolve the initially prepared two-electron states by detecting non-stationary spin-polarized currents flowing in both reservoirs and controlling the residual charge.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.