Antireflective photonic structure for coherent nonlinear spectroscopy of single magnetic quantum dots

This work presents epitaxial growth and optical spectroscopy of CdTe quantum dots (QDs) in (Cd,Zn,Mg)Te barriers placed on the top of (Cd,Zn,Mg)Te distributed Bragg reflector. The formed photonic mode in our half-cavity structure permits to enhance the local excitation intensity and extraction efficiency of the QD photoluminescence, while suppressing the reflectance within the spectral range covering the QD transitions. This allows to perform coherent, nonlinear, resonant spectroscopy of individual QDs. The coherence dynamics of a charged exciton is measured via four-wave mixing, with the estimated dephasing time $T_2=(210\,\pm\,40)$ ps. The same structure contains QDs doped with single Mn$^{2+}$ ions, as detected in photoluminescence spectra. Our work therefore paves the way toward investigating and controlling an exciton coherence coupled, via $s$,$p$-$d$ exchange interaction, with an individual spin of a magnetic dopant.Comment: 6 pages, 5 figure

Bilayer graphene inclusions in rotational-stacked multilayer epitaxial graphene

Additional component in multi-layer epitaxial graphene grown on the C-terminated surface of SiC, which exhibits the characteristic electronic properties of a AB-stacked graphene bilayer, is identified in magneto-optical response of this material. We show that these inclusions represent a well-defined platform for accurate magneto-spectroscopy of unperturbed graphene bilayers.Comment: 5 pages, 2 figures, to appear in Phys. Rev.

Private pension provision in ukraine: state and prospects

Обґрунтовано необхідність впровадження трьохрівневої пенсійної системи. Здійснено аналіз роботи інститутів системи добровільного недержавного пенсійного забезпечення. Визначено розбіжності між суб’єктами недержавного пенсійного забезпечення. The article deals with the necessity of introducing a three level pension system. It analyses the activities of the institutes of private pension provision. The differences between the subjects of private pension provision are determined

Response timing in the lunge and target change in elite versus medium-level fencers.

The aim of the present work is to examine the differences between two groups of fencers with different levels of competition, elite and medium level. The timing parameters of the response reaction have been compared together with the kinetic variables which determine the sequence of segmented participation used during the lunge with a change in target during movement. A total of 30 male sword fencers participated, 13 elite and 17 medium level. Two force platforms recorded the horizontal component of the force and the start of the movement. One system filmed the movement in 3D, recording the spatial positions of 11 markers, while another system projected a mobile target over a screen. For synchronisation, an electronic signal enabled all the systems to be started simultaneously. Among the timing parameters of the reaction response, the choice reaction time (CRT) to the target change during the lunge was measured. The results revealed differences between the groups regarding the flight time, horizontal velocity at the end of the acceleration phase, and the length of the lunge, these being higher for the elite group, as well as other variables related to the temporal sequence of movement. No significant differences have been found in the simple reaction time or in CRT. According to the literature, the CRT appears to improve with sports practice, although this factor did not differentiate the elite from medium-level fencers. The coordination of fencing movements, that is, the right technique, constitutes a factor that differentiates elite fencers from medium-level ones

Structure and Morphology of Nitride Coating (TiHfZrVNb)N After Thermal Annealing 600˚C

This study reports the influence of thermal annealing 600 °C on the characteristics of the (Ti- HfZrVNb)N coatings prepared by vacuum arc melting at different deposition conditions. The crystal structures, surface’s morphology were characterized by X-ray diffraction and atomic force microscopy. The results indicate that nitride coatings based on high-entropy alloy TiHfZrVNb have fcc crystal structure. It is shown that the nitride coatings (TiHfZrVNb)N have a good resistance to oxidation during thermal annealing 600 °C. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3540

Direct measurement of hyperfine shifts and radio frequency manipulation of the nuclear spins in individual CdTe/ZnTe quantum dots

We achieve direct detection of electron hyperfine shifts in individual CdTe / ZnTe quantum dots. For the previously inaccessible regime of strong magnetic fields Bz≳0.1T, we demonstrate robust polarization of a few-hundred-particle nuclear spin bath, with an optical initialization time of ∼1 ms and polarization lifetime exceeding ∼1s. Nuclear magnetic resonance spectroscopy of individual dots reveals strong electron-nuclear interactions characterized by Knight fields |Be|≳50 mT, an order of magnitude stronger than in III–V semiconductor quantum dots. Our studies confirm II–VI semiconductor quantum dots as a promising platform for hybrid electron-nuclear spin qubit registers, combining the excellent optical properties comparable to III–V dots and the dilute nuclear spin environment similar to group-IV semiconductors