Metastable excited states of a closed quantum dot probed by an aluminum single-electron transistor

Kinetics of a closed quantum dot (QD) in a GaAs AlGaAs heterostructure crystal are studied by probing the current through an aluminum single-electron transistor fabricated on top of the QD. Distinctly different characteristics of the Coulomb blockade oscillations are found in different gate bias conditions, indicating different regimes of the isolated QD. An excited state of the QD, where the electrostatic potential is significantly lifted up, as well as another excited state, where the electrostatic potential is significantly pulled down, are suggested. Both of the states are characterized by an extremely long life time roughly about 20 min. A model is proposed to consistently explain these states. © 2006 The American Physical Society

Mid-infrared two photon absorption sensitivity of commercial detectors

We report on broad-band two-photon absorption (TPA) in several commercially available MIR inter-band bulk semiconductor photodetectors with the spectral cutoff in the range of 4.5–6 μm. The highest TPA responsivity of 2x10‾⁵ A−mm²/W² is measured for a nitrogen-cooled InSb photovoltaic detector. Its performance as a two-photon detector is validated by measuring the secondorder interferometric autocorrelation function of a multimode quantum cascade laser emitting at the wavelength of 8 μm

Chiral electroluminescence from thin-film perovskite metacavities

Chiral light sources realized in ultracompact device platforms are highly desirable for various applications. Among active media employed for thin-film emission devices, lead-halide perovskites have been extensively studied for photoluminescence due to their exceptional properties. However, up to date, there have been no demonstrations of chiral electroluminescence with a substantial degree of circular polarization (DCP), being critical for the development of practical devices. Here, we propose a new concept of chiral light sources based on a thin-film perovskite metacavity and experimentally demonstrate chiral electroluminescence with DCP approaching 0.38. We design a metacavity created by a metal and a dielectric metasurface supporting photonic eigenstates with close-to-maximum chiral response. Chiral cavity modes facilitate asymmetric electroluminescence of pairs of left and right circularly polarized waves propagating in the opposite oblique directions. The proposed ultracompact light sources are especially advantageous for many applications requiring chiral light beams of both helicities.Comment: 20 pages, 4 figure

Фольклор как средство изучения английского языка

В научной статье рассматривается влияние фольклора на процесс изучения английского языка, собрана и проанализирована теоретическая база по теме. В результате, разработаны практические упражнения с использованием поэтического народного творчества (пословицы, скороговорки, загадки и др.)The scientific article examines the influence of folklore on the process of learning English, collects and analyses the theoretical basis on the topic. As a result, practical exercises have been developed using poetic folk art (proverbs, tongue twisters, riddles, etc.

Применение песен в обучении иностранным языкам

Целью данного исследования является изучение и анализ существующих методик обучения английскому языку с помощью песен для последующего описания наиболее эффективной методики обучения. Для достижения поставленной цели были выявлены преимущества использования музыки и песен во время обучения иностранным языкам на примере английского, и сформирована полная методика обучения с помощью песен.The purpose of this research is to investigate and analyse existing methods of teaching English by listening to songs in order to provide a more detailed description of the most effective teaching method. To accomplish the purpose, the benefits of using music and songs during the teaching of foreign languages in English were examined, and the comprehensive method of teaching using songs was developed

The dependence of dijet production on photon virtuality in ep collisions at HERA

The dependence of dijet production on the virtuality of the exchanged photon, Q^2, has been studied by measuring dijet cross sections in the range 0 < Q^2 < 2000 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb^-1. Dijet cross sections were measured for jets with transverse energy E_T^jet > 7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame in the range -3 < eta^jet <0. The variable xg^obs, a measure of the photon momentum entering the hard process, was used to enhance the sensitivity of the measurement to the photon structure. The Q^2 dependence of the ratio of low- to high-xg^obs events was measured. Next-to-leading-order QCD predictions were found to generally underestimate the low-xg^obs contribution relative to that at high xg^obs. Monte Carlo models based on leading-logarithmic parton-showers, using a partonic structure for the photon which falls smoothly with increasing Q^2, provide a qualitative description of the data.Comment: 35 pages, 6 eps figures, submitted to Eur.Phys.J.

Beauty photoproduction measured using decays into muons in dijet events in ep collisions at s\sqrt{s}=318 GeV

The photoproduction of beauty quarks in events with two jets and a muon has been measured with the ZEUS detector at HERA using an integrated luminosity of 110 pb$^{- 1}$. The fraction of jets containing b quarks was extracted from the transverse momentum distribution of the muon relative to the closest jet. Differential cross sections for beauty production as a function of the transverse momentum and pseudorapidity of the muon, of the associated jet and of $x_{\gamma}^{jets}$, the fraction of the photon's momentum participating in the hard process, are compared with MC models and QCD predictions made at next-to-leading order. The latter give a good description of the data.Comment: 32 pages, 6 tables, 7 figures Table 6 and Figure 7 revised September 200

Search for a narrow charmed baryonic state decaying to D^*+/- p^-/+ in ep collisions at HERA

A resonance search has been made in the D^*+/- p^-/+ invariant-mass spectrum with the ZEUS detector at HERA using an integrated luminosity of 126 pb^-1. The decay channels D^*+ -> D^0 pi^+_s -> (K^- pi^+) pi^+_s and D^*+ -> D^0 pi^+_s -> (K^- pi^+ pi^+ pi^-) pi^+_s (and the corresponding antiparticle decays) were used to identify D^*+/- mesons. No resonance structure was observed in the D^*+/- p^-/+ mass spectrum from more than 60000 reconstructed D^*+/- mesons. The results are not compatible with a report of the H1 Collaboration of a charmed pentaquark, Theta^0_c.Comment: 22 pages, 7 figures, 1 table; minor text revisions; 2 references adde