Topological photonics offers unique functionalities in light manipulation at the nanoscale by means of the so-called topological states which are robust against various forms of disorder. One of the simplest one-dimensional models supporting topological states is the Su–Schrieffer–Heeger model. In this paper, we review the physics of the Su–Schrieffer–Heeger model and its nonlinear counterparts exhibiting self-induced, tunable and many-particle edge states. We discuss the robustness of these states, highlighting their rich potential for nanophotonic and quantum optics applications.

Calculations of the magnetic field required to reverse the magnetization of islands with out-of-plane anisotropy are carried out using a model describing nucleation followed by rapid domain wall motion. The calculations are based on an extension of the Stoner–Wohlfarth model where thermal activation is taken into account as well as the applied magnetic field. The calculated switching field distribution (SFD) is compared with recently reported experimental measurements of de Vries et al. [New J. Phys. 19, 093019 (2017)] on circular 220 nm CoPt islands. The measured results can be closely reproduced by choosing appropriate values of two parameters, the nucleation volume, and the effective anisotropy. Both the position of SDF peaks and their width at high and low temperature, 300 K and 10 K, are amply described using the same set of parameter values for a given island, while there is a large difference between islands with weak and strong magnetic anisotropies. There is no need to introduce the temperature dependence of the activation energy at zero field. This is in contrast with the estimates obtained from the so-called diamond model used by de Vries et al. in their data analysis where multiple adjustable parameters are introduced, and a three- to fourfold change in the zero field activation energy is invoked.

In PCs, the number of arithmetic operations, the comparator is a vital equipment unit, consisting of complementary metal-oxide-semiconductor (CMOS) technology. Another procedure, referred to as Quantum Cellular Automata (QCA) will supplant the CMOS outlines, having leverage concerning zone, control utilization, and latency. The primary QCA circuits planned with the inverter and majority voter entryways. In this paper, we utilize the clocking method 180 out of phase clock crossover to outline the 1-bit comparator and compare with the current outcomes. The new proposed wire crossing plan lessens the quantity of cells required to configuration, power and area necessities. Additionally, we planned 2-bit comparator having 11 majority gates (voters), 2 number of crossovers with 0.38 µm² area, 203 number of cells. The designed 1-bit comparator contrast and the past outcomes where cells, region, delay demonstrates 53.57 %, 50 % and 33.32 % improvement respectively.

The interaction of electrons in a superlattice with electromagnetic radiation in presence of static electric and magnetic fields is investigated. The electric field is directed along the superlattice axis while the magnetic field is inclined at an arbitrary angle to the axis of superlattice. It is shown that the dependence of current in the superlattice on electric field in the general case can have several maxima. In some regions of electric and magnetic field values, the absorption coefficient for high frequency electromagnetic radiation can be negative that means the electromagnetic wave will be amplified. We note that negative absorption in the system is possible at some conditions at the region of positive differential conductivity in contrast to classical Bloch oscillator in which amplification takes place in case of negative differential conductivity only. This phenomenon can be used for the design of a teraherz amplifier and generator based on the superlattice.

Determining the atomic structure of nanoclusters is a challenging task and a critical one for understanding their chemical and physical properties. Recently, the high resolution aberration corrected scanning transmission electron microscope (AC-STEM) technique has provided valuable information about such systems, but the analysis of the experimental images has typically been qualitative rather than quantitative. A method is presented for detailed analsis of AC-STEM images combined with theoretical modelling to extract atomic coordinates. An objective function formed by a linear combination of a fit to the two-dimensional AC-STEM image plus an estimate of the cluster’s energy for adding information about the third dimension is used in a global optimization algorithm to extract the atomic coordinates. The method is illustrated by analyzing model images generated for the Garzón structure of the Au₅₅ cluster, which is a metastable structure for the embedded atom method (EAM) potential function used here to estimate the total energy. As the method does not rely on the alignment of atom rows in the AC-STEM image, the partially disordered chiral structure of the Au₅₅ can successfully be determined even when a significant level of noise is added to the images.

We propose a new combination of an anionic (potassium oleate) and cationic (n-octylpyridinium chloride) surfactants that are able to self-assemble into long cylindrical (wormlike) mixed micelles in water. The solutions have strong viscoelastic properties with viscosity up to 300 Pa·s and elastic modulus around 20 Pa, which are attributed to the formation of an entangled micellar network. We discover that with an increase in the molar ratio of cationic to anionic surfactant, the solutions first increase drastically their viscosity and elasticity due to the growth of micelles in length and formation of the network, but then the rheological parameters slightly decrease, possibly due to micellar branching or shortening. The addition of cationic surfactant also induces the increase of difference between scission energy and micellar electrostatic energy, which is explained both by stronger binding of surfactants within the micelle and decrease of the micellar net charge.

Kinetic coefficients of semiconductor superlattice are obtained from the Boltzmann transport equation with Bhatnagar–Gross–Krook (BGK) collision term and Poisson equation. Using the universal analytic procedure, we found kinetic coefficient in the quasistatic limit starting from the exact solution of the Boltzmann transport equation. It is shown that the Einstein relation for the diffusion coefficient is applicable only for weak fields and it is not valid in the general case. As a consequence, a drift-diffusion model of miniband transport in the case of strong dc and ac fields should be corrected, taking into account the kinetic coefficients obtained from the Boltzmann equation.

A method is presented for finding instantons in magnetic systems – optimal paths corresponding to tunneling from one magnetic state to another at a finite temperature. The method involves analytical continuation of the energy to allow for complex values of the angle variables. First, a set of discretization points are placed equally spaced on a chosen energy contour. Then, an estimate of the corresponding temperature is obtained using Landau-Lifshitz dynamics in imaginary time along the contour. Finally, the distribution of the discretization points as well as the energy are systematically refined by converging on the nearest stationary point of the Euclidean action, thereby obtaining a discrete representation of the closest instanton at the given temperature. The method is illustrated with an application to a system consisting of a single spin subject to uniaxial anisotropy and transverse external magnetic field. First-order and second-order crossovers from over-the-barrier mechanism to tunneling are found depending on the applied field, and the difference in the dependence of the instanton temperature on the energy illustrated for the two cases. By comparing the Boltzmann factors for over-the-barrier and tunneling transitions, the crossover temperature between the two mechanisms is estimated for both first- and second-order crossover.

Ceria nanoparticles are capable of performing the function of some enzymes (such as oxidoreductases, phosphatase) and can be classified as nanozymes. In this review, the actual data on the enzymatic activity of ceria were critically analyzed and specific conditions under which the cerium dioxide nanoparticles can act as enzymes were defined. The presented analysis may be useful in the planning, design and synthesis of ceria nanoparticles having the desired enzymatic functions required for various processes, including the development of the nanodrugs, which exhibit the therapeutic effect depending on their composition and pH of media, development of molecular sensors and biosensors, etc.

High cost conducting metals such as Au or Pt are generally used as counter electrodes in quantum dot sensitized solar cells. In this article, we report working of a CdS quantum dot sensitized ZnO thin film solar cell, having FTO as working electrode and aluminium as counter electrode. The CdS quantum dots are prepared by simple low cost chemical technique and characterized by absorption spectroscopy, X-ray diffraction, atomic force microscopy and high resolution trans electron microscopy. These quantum dots are used as an active layer in a solar cell and current density–voltage characteristic of the solar cell is obtained under white light illumination and dark conditions.

Cost-effective route to quaternary Cu₂ZnSnS₄ nanostructured powder fabrication was developed by utilizing a two-step approach. In the first stage, nanostructured binary sulfides Cu₂S, ZnS, and SnS were synthesized by chemical bath deposition. In the second stage, ternary sulfide Cu₂ZnSnS₄ was obtained by low-temperature annealing of binary sulfides’ mixtures at 70 and 300 ^◦C. The compounds obtained on both stages were investigated by X-ray diffraction, scanning electron microscopy, optical absorbance and Raman spectroscopy. On the basis of our findings, we established that Cu₂ZnSnS₄ phase has already formed at 300 ^◦C. The synthetic pathway revealed in this work allows reducing the temperature of Cu₂ZnSnS₄ synthesis and as a result, offers the possibility of reducing the manufacturing costs. This work was supported by the Russian Foundation for Basic Research (grant No. 16-03-00566), UrB RAS (grant No.15-20-3-11).

The generation of laser radiation by a nanostructured solid active element with natural selective optical nanoresonator formed in a nanoporous aluminum oxide film activated with rhodamine 6G has been obtained for the first time. The lasing is characterized by high-quality radiation with the absence of a spontaneous component. Chemical deposition of noble metals leads to the formation of internal nanoresonator into the porous structure. This reduces generation threshold more than two fold.

We report the application of porous polypropylene hollow fiber membranes with 100×500 nm slit pores in membrane contactor for air dehumidification using triethylene glycol (TEG) as an absorbent. Experiment geometry with gas flow through the lumen of fiber and absorbent circulated on the shell side was utilized to enhance water vapor stage cut. The influence of gas flow rate, liquid circulation rate and water content in triethylene glycol solution on the performance of membrane contactor was studied. The obtained results reveal that the limiting step of water vapor absorption for lumen gas flow configuration is the diffusion of water into TEG volume. Using dry TEG solution and high circulation rate the dew point of feed gas can be decreased down to ∼ −30 ^◦C for the membrane contactor performance of 30 – 60 l/(m²h), while with reducing dew point requirements to −10 ^◦C the performance of the contactor over 1 m³/(m²h) is achievable.

Nanostructured hybrid Ni–CN_x films were grown by magnetron sputtering of a composite graphite-nickel target. Atomic force microscopy showed the clustered nature of the films deposition on the substrate surface: a relatively high pressure in the low-temperature magnetron plasma made it possible to form the Ni@CN_x nanoclusters type “core-shell”, where metallic nickel is the core and carbon nitride is the shell. When studying the role of carbon in the formation of the structure and properties of Ni@CN_x nanoclusters, it was established that the saturation magnetization 4πM_s of nanoclusters drops sharply with a carbon content above 30 at.%. The reason is the formation of an increasingly saturated solid solution of carbon in nickel. At a carbon concentrations above 38 at.%, amorphous Ni–CN_x nanoclusters are formed in the magnetron plasma, which are deposited on the substrate. An increase in the substrate temperature leads to the crystallization of Ni atoms, and the C and N atoms are forced out onto the surface of the nickel core, forming an array of Ni@CN_x elements.

Fractal analysis has emerged as a potential analytical tool in almost all branches of science and technology. The paper is the first report of using fractal dimension as a surrogate technique for estimating particle size. A regression equation is set connecting the soot particle size and fractal dimension, after investigating the Field Emission Scanning Electron Microscopic (FESEM) images of carbonaceous soot from five different sources. Since the fractal dimension is an invariant property under the scale transformation, an ordinary photograph of the soot should also yield the same fractal dimension. This enables one to determine the average size of the soot particles, using the regression equation, by calculating the fractal dimension from the photograph. Hence, instead of frequent measurement of average particle size from FESEM, this technique of estimating the particle size from the fractal dimension of the soot photograph, is found to be a potentially cost-effective and non-contact method.

A new stable Ti₉O₁₀ nanophase (sp. gr. Immm) has been detected by X-ray diffraction (XRD) after high energy ball milling and long-term vacuum annealing of nanocrystalline powder of nonstoichiometric disordered and ordered titanium monoxide TiO_y with B1 structure (sp. gr. Fm3̄m). With the help of XRD data, the unit cell of the Ti₉O₁₀ nanophase as well as the distribution of atoms and structural vacancies in the titanium and oxygen sublattices of this phase have been established. The crystal structure of Ti₉O₁₀ is derived from that of TiO_y by (a) a migration of the vacancies to the specific crystallographic planes of B1 structure and (b) by orthorhombic distortions. The DFT calculations of the full energy of the coarse-crystalline phases TiO_y and Ti₉O₁₀ revealed that the bulk ordered phase Ti₉O₁₀ is not preferable in comparison with the bulk disordered cubic phase TiO_y with the same content of vacancies in the sublattices, so, it is the nanostate that causes the formation of Ti₉O₁₀.

In the present paper we report utilization of porous and barrier type of titania films formed by anodic oxidation as an active layer of the memristive element in the Au–TiO₂–Ti structure. The comparison of semiconductor properties of porous and barrier type of anodic titania was performed via the Mott–Schottky technique. The obtained memristive elements show the bipolar type of switching governed by Schottky barrier screening. For barrier type film the switching potential is equal to −1.5 V and the ratio of resistance in OFF and ON stage (R_off /R_on) is equal to 34. For porous type films, the switching potential is equal to −0.6 V and R_off /R_on = 131. Moreover, we observed the dependence of R_off /R_on on the voltage sweeping rate, which can be explained by the limitation in diffusion of oxygen vacancies through the oxide layer.

The phase diagram of the NaF–SrF₂ system was studied by thermal analysis and X-ray powder diffraction analysis with the determination of the chemical composition. The system was found to be of the eutectic type. The eutectic co-ordinates are 853 ^◦C, 32 mol % SrF₂. A narrow range of the existence of solid solution Sr_1−xNa_xF_2−x was established. The NaF solubility reaches a maximal value of x = 0.035 at eutectic temperature. The solubility of KF in SrF₂ is very low.

Effect of magnetic field application on phase transition in nanostructured solid solutions (1 − x)KH₂PO₄ – (x)(NH₄)H₂PO₄ at x = 0, 0.05 and 0.15 has been studied by dielectric spectroscopy at B = 0 − 10T. The samples have been prepared by impregnation of magnetic porous glasses by KDP-ADP solid solutions. The average pore diameter in glasses was 50(5) nm. The temperatures of the ferroelectric phase transition have been determined, and the phase diagrams for these nanocomposite materials (NCM) on cooling and heating (including at magnetic field application) were constructed. The interface “matrix-nanoparticles” was shown to play the principal role in phase diagram formation.