Depending on the Ginzburg-Landau parameter κ, superconductors can either be fully diamagnetic if (type I superconductors) or allow magnetic flux to penetrate through Abrikosov vortices if (type II ...superconductors; refs 1, 2). At the Bogomolny critical point, , a state that is infinitely degenerate with respect to vortex spatial configurations arises3, 4. Despite in-depth investigations of conventional type I and type II superconductors, a thorough understanding of the magnetic behaviour in the near-Bogomolny critical regime at κ ∼ κc remains lacking. Here we report that in confined systems the critical regime expands over a finite interval of κ forming a critical superconducting state. We show that in this state, in a sample with dimensions comparable to the vortex core size, vortices merge into a multi-quanta droplet, which undergoes Rayleigh instability5 on increasing κ and decays by emitting single vortices. Superconducting vortices realize Nielsen-Olesen singular solutions of the Abelian Higgs model, which is pervasive in phenomena ranging from quantum electrodynamics to cosmology6, 7, 8, 9. Our study of the transient dynamics of Abrikosov-Nielsen-Olesen vortices in systems with boundaries promises access to non-trivial effects in quantum field theory by means of bench-top laboratory experiments.
Advanced mechanical properties of ODS steels are mainly due to the high number density of homogeneously distributed oxide inclusions. It is well known that some alloying elements like Ti, V, Zr, … ...play important role in oxide/nanocluster formation and influence on number density and size of these inclusions. In this work, we studied an ODS steel contained both vanadium and titanium. The ODS 12Cr-1.1W-0.2V-0.3Ti steel was characterized with TEM and APT. Different types of oxides inclusions were revealed in the steel: large (>70 nm) Ti
2
O
3
oxides, small (~ 2–15 nm) Y-Ti-O oxides, and nanoclusters (2–5 nm). It was shown that the number density of these nanoclusters was considerably high than the one of the oxides and nanoclusters are enriched in Y, O, Cr, Ti, and V. Moreover, in spite of the fact that V and Ti are present in the material in approximately close value, clusters are predominantly enriched in Ti. APT samples of this material were irradiated with Fe ions up to ~ 8 dpa at room temperature. APT analysis of the irradiated material revealed decreasing of nanocluster number density with increasing their sizes. Changing in nanocluster composition was detected after the irradiation, but the decrease of Ti concentration in clusters was considerably less than the one for V. However, the Y/Ti, Y/(Ti + V), and (Ti + V + Y)/O composition ratios of nanoclusters remained stable under Fe ion irradiation to 8 dpa at room temperature.
The article is devoted to development of fatigue failure criterion of the CFRP specimen under fatigue tension loading. The main goal of the current study is to develop a quantitative failure ...criterion for fatigue damage of a specimen with open hole under tension. In response to this problem, the influence of the following parameters on the stability of the criterion and on its application was determined experimentally: manufacturing technology of a material, the loading conditions during testing. The usage of the failure criterion of thickening in the hole zone made it possible to obtain S-N curve while using the classical criterion does not allow to get a S-N curve at some cases. The application of developed failure criterion of thickening made it possible to reduce the standard deviation of the logarithm of SlgN durability. The dependence of the matrix damage area around the hole from the endurance at different loading levels was obtained according to the results of NDT method.
The characterization of the nanostructure of modern oxide dispersion strengthened steels requires a comprehensive analysis using complementary techniques. In this work, the methods of small-angle ...X-ray scattering, transmission electron microscopy and atom probe tomography have been applied to several oxide dispersion strengthened steels. Comparison of the obtained results allows the most correct characterization of inclusion types and their number in the studied materials. It is shown that most of the studied steels contain oxide inclusions and nanosized clusters enriched in O and Y, as well as V, Ti, Al, and Zr, depending on the initial steel composition. Transmission electron microscopy and atom probe tomography provide detailed information about the inclusion types, and small-angle X-ray scattering gives the most accurate estimation of the average density of inclusions in large volumes of material. The importance of the correct determination of the inclusion types for hardening calculations is shown, the results of such calculations are compared with microhardness measurements. The calculated values of hardness for the studied steels are in the range 2.7–4.3 GPa, which is well confirmed by microhardness measurements.
The ability to synthesize VO2 in the form of single-crystalline nanobeams and nano- and microcrystals uncovered a number of previously unknown aspects of the metal−insulator transition (MIT) in this ...oxide. In particular, several reports demonstrated that the MIT can proceed through competition between two monoclinic (insulating) phases M1 and M2 and the tetragonal (metallic) R phase under influence of strain. The nature of such phase behavior has been not identified. Here we show that the competition between M1 and M2 phases is purely lattice-symmetry-driven. Within the framework of the Ginzburg−Landau formalism, both M phases correspond to different directions of the same four-component structural order parameter, and as a consequence, the M2 phase can appear under a small perturbation of the M1 structure such as doping or stress. We analyze the strain-controlled phase diagram of VO2 in the vicinity of the R−M2−M1 triple point using the Ginzburg−Landau formalism and identify and experimentally verify the pathways for strain-control of the transition. These insights open the door toward more systematic approaches to synthesis of VO2 nanostructures in desired phase states and to use of external fields in the control of the VO2 phase states. Additionally, we report observation of the triclinic T phase at the heterophase domain boundaries in strained quasi-two-dimensional VO2 nanoplatelets, and theoretically predict phases that have not been previously observed.
Optical Anapoles: Concepts and Applications Baryshnikova, Kseniia V.; Smirnova, Daria A.; Luk'yanchuk, Boris S. ...
Advanced optical materials,
07/2019, Letnik:
7, Številka:
14
Journal Article
Odprti dostop
Interference of electromagnetic modes supported by subwavelength photonic structures is one of the key concepts that underpins the nanoscale control of light in metaoptics. It drives the whole realm ...of all‐dielectric Mie‐resonant nanophotonics with many applications for low‐loss nanoscale optical antennas, metasurfaces, and metadevices. Specifically, interference of the electric and toroidal dipole moments results in a very peculiar, low‐radiating optical state associated with the concept of optical anapole. Here, the physics of multimode interferences and multipolar interplay in nanostructures is uncovered with an intriguing example of the optical anapole. The recently emerged field of anapole electrodynamics is reviewed, explicating its relevance to multipolar nanophotonics, including direct experimental observations, manifestations in nonlinear optics, and rapidly expanding applications in nanoantennas, active photonics, and metamaterials.
This review uncovers the physics of multimode interference and multipolar interplay in subwavelength photonics with an intriguing example of “optical anapoles”—specific optical states manifested as far‐field scattering suppression accompanied with considerable local field enhancement. The anapole effect underlies a plethora of recent experimental observations and perspective applications in nanophotonics and metaoptics.
PDF
