Nonlinear emission dynamics of a GaAs microcavity with embedded quantum wells

The emission dynamics of a GaAs microcavity at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond-pulse excitation is measured. At sufficiently high excitation densities, the decay time of the lower-polariton emission increases with the polariton wavevector; at low excitation densities the decay time is independent of the wavevector. The effect of additional nonresonant continuous illumination on the emission originating from the bottom of the lower polariton branch is investigated. The additional illumination leads to a substantial increase in the emission intensity (considerably larger than the intensity of the photoluminescence excited by this illumination alone). This fact is explained in terms of acceleration of the polariton relaxation to the radiative states due to scattering by charge carriers created by the additional illumination. The results obtained show, that at large negative detunings between the photon and exciton modes, polariton-polariton and polariton-free carrier scattering are the main processes responsible for the filling of states near the bottom of the lower polariton branch.Comment: 10 pages, 6 figures. This is an author-created, un-copyedited version of an article accepted for publication in Journal of Physics: Condesed Matter. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

The nature of the ferromagnetic ground state in the Mn4 molecular magnet

Using ab initio band structure and model calculations we studied magnetic properties of one of the Mn$_4$ molecular magnets (Mn4(hmp)6), where two types of the Mn ions exist: Mn3+ and Mn2+. The direct calculation of the exchange constants in the GGA+U approximation shows that in contrast to a common belief the strongest exchange coupling is not between two Mn3+ ions (J_{bb}), but along two out of four exchange paths connecting Mn3+ and Mn2+ ions (J_{wb}). The microscopic analysis performed within the perturbation theory allowed to establish the mechanism for this largest ferromagnetic exchange constant. The charge ordering of the Mn ions results in the situation when the energy of the excited state in the exchange process is defined not by the large on-site Coulomb repulsion U, but by much smaller energy V, which stabilizes the charge ordered state. Together with strong Hund's rule coupling and specific orbital order this leads to a large ferromagnetic exchange interaction for two out of four Mn2+ --Mn3+ pairs.Comment: 12 pages, 10 figure

Resonant photoemission at the absorption edge of Mn and Ti and electronic structure of 1T-Mn0.2_{0.2}TiSe2_2

Resonant valence-band X-ray photoelectron spectra (ResPES) excited near 2p$_{3/2}$ core level energies, 2p X-ray photoelectron spectra (XPS) and L$_{3,2}$ X-ray absorption spectra (XAS) of Ti and Mn in single crystal of 1T-Mn$_2$TiSe$_2$ were studied for the first time. The ionic-covalent character of bonds formed by Mn atoms with the neighboring Se atoms in the octahedral coordination is established. From the XPS and XAS measurements compared with results of atomic multiplet calculations of Ti and Mn L$_{3,2}$ XAS it is found that Ti atoms are in ionic state of 4+ and Mn atoms are in the state of 2+. In ResPES of Mn$_{0.2}$TiSe$_2$ excited near Ti 2p$_{3/2}$ and Mn 2p$_{3/2}$ absorption edges the Ti 3d and Mn 3d bands at binding energies just below the Fermi level are observed. According to band structure calculations E$(\textbf{k})$ the Ti 3d states are localized in the vicinity of $\mathsf{\Gamma}$ point and the Mn 3d states are localized along the direction K-$\mathsf{\Gamma}$-M in the Brillouin zone of the crystal.Comment: 18 pages (preprint), 9 figure

Band structure approach to the resonant x-ray scattering

We study the resonance behaviour of the forbidden 600 and 222 x-ray Bragg peaks in Ge using LDA band structure methods. These Bragg peaks remain forbidden in the resonant dipole scattering approximation even taking into account the non local nature of the band states. However they become allowed at resonance if the eigenstates of the unoccupied conduction band involve a hybridization of p like and d like atomic states. We show that the energy dependence of the resonant behaviour, including the phase of the scattering, is a direct measure of this p-d hybridization.and obtain quantitative agreement with experiment. A simple physical picture involving a product of dipole and quadrupolar transition matrix elements explains this behaviour and shows that it should be generally true for cases where the resonating atom is not at an inversion center. This has strong implications for the description of the resonance behavior of x-ray scattering in materials where the resonant atom is not at an inversion center such as V2O3 and in ferro and antiferro electric and piezo electric materials in general.Comment: 4 pages, 5figure

Correlation effects in Ni 3d states of LaNiPO

The electronic structure of the new superconducting material LaNiPO experimentally probed by soft X-ray spectroscopy and theoretically calculated by the combination of local density approximation with Dynamical Mean-Field Theory (LDA+DMFT) are compared herein. We have measured the Ni L2,3 X-ray emission (XES) and absorption (XAS) spectra which probe the occupied and unoccupied the Ni 3d states, respectively. In LaNiPO, the Ni 3d states are strongly renormalized by dynamical correlations and shifted about 1.5 eV lower in the valence band than the corresponding Fe 3d states in LaFeAsO. We further obtain a lower Hubbard band at -9 eV below the Fermi level in LaNiPO which bears striking resemblance to the lower Hubbard band in the correlated oxide NiO, while no such band is observed in LaFeAsO. These results are also supported by the intensity ratio between the transition metal L2 and L3 bands measured experimentally to be higher in LaNiPO than in LaFeAsO, indicating the presence of the stronger electron correlations in the Ni 3d states in LaNiPO in comparison with the Fe 3d states in LaFeAsO. These findings are in accordance with resonantly excited transition metal L3 X-ray emission spectra which probe occupied metal 3d-states and show the appearance of the lower Hubbard band in LaNiPO and NiO and its absence in LaFeAsO.Comment: 6 pages, 5 figure

Classification of the electronic correlation strength in the Fe-pnictides: The case of the parent compound BaFe2As2

Electronic correlations in the Fe-pnictide BaFe2As2 are explored within LDA+DMFT, the combination of density functional theory with dynamical mean-field theory. While the correlated band structure is substantially renormalized there is only little transfer of spectral weight. The computed k-integrated and k-resolved spectral functions are in good agreement with photoemission spectroscopy (PES) and angular resolved PES experiments. Making use of a general classification scheme for the strength of electronic correlations we conclude that BaFe2As2 is a moderately correlated system.Comment: 4 pages, 3 figure

Общие принципы вакцинации пациентов с нервно-мышечными болезнями

Vaccination is recognized as the most effective, safe, and cost-effective way to prevent infectious diseases and their complications. For patients with chronic diseases, and for patients with neuromuscular diseases in particular, vaccination is the highest priority for the prevention of infectious diseases. In the current literature, there is a lack of information describing the principles of vaccination of patients with spinal muscular atrophy and Duchenne muscular dystrophy. In patients with neuromuscular diseases, full immunization has to be done in accordance with the National calendar and recommendations with the introduction of an additional vaccine against such diseases as: rotavirus infection, pneumococcal infection (using an additional dose of 23-valent vaccine), meningococcal infection, virus human papilloma, respiratory viral infection. syncytial virus and influenza. In this regard, of particular importance is the development of recommendations describing the schemes for the use of vaccines in children suffering from spinal muscular atrophy and Duchenne muscular dystrophy.Вакцинация признана самым эффективным, безопасным и экономически выгодным способом профилактики инфекционных заболеваний и их осложнений. Для пациентов с хроническими болезнями и с нервно-мышечными заболеваниями в частности вакцинация является наиболее приоритетным методом профилактики инфекционных заболеваний. В современной литературе наблюдается дефицит информации, описывающей принципы вакцинации пациентов со спинальной мышечной атрофией и прогрессирующей мышечной дистрофией Дюшенна. Пациентам с нервно-мышечными заболеваниями показана иммунизация в полном объеме в соответствии с Национальным календарем с введением дополнительных вакцин против таких заболеваний, как ротавирусная инфекция, пневмококковая инфекция (с использованием дополнительных доз 23-валентной вакцины), менингококковая инфекция, вирус папилломы человека, респираторно-синцитиальный вирус и вирус гриппа. В связи с этим особую важность имеет разработка рекомендаций, описывающих схемы применения вакцин у детей, страдающих спинальной мышечной атрофией и прогрессирующей мышечной дистрофией Дюшенна

Importance of implementation disease prevention programs temporomandibular joint in elderly and senile

The aim of the study was to increase the effectiveness of prevention of dysfunctional states of the temporomandibular joint (TMJ) in elderly and senile age by developing and implementing new approaches to health education as part of the creation and implementation of the program «Prevention of diseases of the temporomandibular joint in elderly and senile». To achieve the objectives were examined 86 patients from 60 to 83 years: 25 patients with symptoms of diseases TMJ found as a result of uptake with complaints of difficulty in chewing, aesthetic dissatisfaction, and 61 patients who were sent for consultation gnathology doctors another profile under the program "Prevention of diseases of the temporomandibular joint in elderly and senile.