Landau–Zener–Stückelberg interferometry

A transition between energy levels at an avoided crossing is known as a Landau–Zener transition. When a two-level system (TLS) is subject to periodic driving with sufficiently large amplitude, a sequence of transitions occurs. The phase accumulated between transitions (commonly known as the Stückelberg phase) may result in constructive or destructive interference. Accordingly, the physical observables of the system exhibit periodic dependence on the various system parameters. This phenomenon is often referred to as Landau–Zener–Stückelberg (LZS) interferometry. Phenomena related to LZS interferometry occur in a variety of physical systems. In particular, recent experiments on LZS interferometry in superconducting TLSs (qubits) have demonstrated the potential for using this kind of interferometry as an effective tool for obtaining the parameters characterizing the TLS as well as its interaction with the control fields and with the environment. Furthermore, strong driving could allow for fast and reliable control of the quantum system. Here we review recent experimental results on LZS interferometry, and we present related theory.     

Electrochemical behavior of silicon compound in LiF–NaF–KF–Na<Subscript>2</Subscript>SiF<Subscript>6</Subscript> molten salt

The electrochemical reduction and nucleation process of Si⁴⁺ on an electrical steel electrode in the eutectic LiF–NaF–KF molten salt were investigated at 750 °C, by means of cyclic voltammetry and chronoamperometry technique. Silicon was electrodeposited on steel, and Fe₃Si was formed by the diffusivity of silicon on the electrode surface. The electrochemical reduction of Si⁴⁺ process in single-step charge transfer and the cathode process was reversible. The electrocrystallization process of silicon is controlled by progressive three-dimensional mechanism. The diffusion coefficient was calculated to be 5.42 × 10⁻⁷ cm²/s by chronopotentiometry at experimental conditions.     

Stability of Zn–Ni–TiO<Subscript>2</Subscript> and Zn–TiO<Subscript>2</Subscript> nanocomposite coatings in near-neutral sulphate solutions

Zn–Ni–TiO₂ and Zn–TiO₂ nanocomposites were prepared by galvanostatic cathodic square wave deposition. X-ray diffraction analysis and scanning electron microscopy revealed that the occlusion of TiO₂ nanoparticles (spherical shaped with diameter between 19.5 and 24.2 nm) promotes the formation of the γ-Ni₅Zn₂₁ phase, changes the preferred crystallographic orientation of Zn from (101) and (102) planes to (002), and decreases the particle size of the metallic matrices. The stability of the nanocomposites immersed in near-neutral 0.05 mold m⁻³ Na₂SO₄ solution (pH 6.2) was investigated over 24 h. The initial open circuit potential for the Zn–Ni–TiO₂ and Zn–TiO₂ coatings were −1.32 and −1.51 V (vs. Hg/Hg₂SO₄), respectively, and changed to −1.10 and –1.49 V (vs. Hg/Hg₂SO₄) after 24 h of immersion. Data extracted from the steady state polarization curves demonstrated that the metal–TiO₂ nanocomposites have, with respect to the metal coatings, a higher corrosion potential in the case of the Zn–Ni alloy composite; a lower corrosion potential in the case of Zn-based nanocomposite albeit the predominant (002) crystallographic orientation; and a lower initial corrosion resistance due to the smaller grain size and higher porosity in the Zn–Ni–TiO₂ and Zn–TiO₂ nanocomposites. Morphological and chemical analyses showed that a thicker passive layer is formed on the surface of the Zn–Ni–TiO₂ and Zn–TiO₂ deposits. After 24 h of immersion in the sulphate solution, the Zn–Ni–TiO₂ coating has the highest corrosion stability due to the double-protective action created by the deposit’s surface enrichment in Ni plus the higher amount of corrosion products.     

Phase formation in the BaCO<Subscript>3</Subscript>–PbO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> system

Features of the formation of lead-ferroniobate compounds in the xBaCO₃–(1 – x)PbO–Fe₂O₃–Nb₂O₅ system by solid-phase synthesis are investigated. For perovskite-type lead-ferroniobate solid solution, a single-phase concentration region is revealed at 1233 K. The crystalline structures of the synthesized compounds are refined using Rietveld analysis and the Pm3?m and R3m space groups. Ceramic samples of lead ferroniobate are studied by scanning electron microscopy.     

Lagrange–Poincaré field equations

The Lagrange–Poincaré equations of classical mechanics are cast into a field theoretic context together with their associated constrained variational principle. An integrability/reconstruction condition is established that relates solutions of the original problem with those of the reduced problem. The Kelvin–Noether Theorem is formulated in this context. Applications to the isoperimetric problem, the Skyrme model for meson interaction, and molecular strands illustrate various aspects of the theory.     

Size-controllable synthesis of functional heterostructured TiO<Subscript>2</Subscript>–WO<Subscript>3</Subscript> core–shell nanoparticles

Mono and bicomponent TiO₂ and WO₃ nanoparticles were synthesized inside Vycor^® glass pores, by cycles of impregnation of the glass with the respective oxide precursor followed by its thermal decomposition. The impregnation-decomposition cycle (IDC) methodology promoted a linear mass increase of the glass matrix, and allowed tuning the nanoparticle size. X-ray diffraction and Raman spectroscopy data allowed identifying the formation of TiO₂ as anatase phase, while WO₃ is a mixture of the γ-WO₃ (monoclinic) and δ-WO₃ (triclinic) phases. High resolution transmission electron microscopy images revealed that for 3, 5, and 7 IDC, the TiO₂ nanoparticles obtained presented average diameters of 3.4, 4.3, and 5.1 nm, and the WO₃ nanoparticles have 2.9, 4.6, and 5.7 nm sizes. These TiO₂ and WO₃ monocomponent nanoparticles were submitted to IDC with the other oxide precursor, resulting in bicomponent nanoparticles. The broadening and shift of the Raman bands related to titanium and tungsten oxides suggest the formation of hetero-structure core–shell nanoparticles with tunable core sizes and shell thicknesses.     

Electrooptical effect in the plasmon structure glass–In<Subscript>2</Subscript>O<Subscript>3</Subscript>: Sn–ferroelectric–Al with a subwavelength grating

We have constructed the equations of state for crystalline boron carbide B₁₁C (C–B–C) and its melt under high dynamic and static pressures. A kink on the shock adiabat for boron carbide has been revealed in the pressure range near 100 GPa, and the melting curve with negative curvature in the pressure range 0–120 GPa has been calculated. The results have been used for interpreting the kinks on the shock adiabat for boron carbide in the pressure range of 0–400 GPa.     

The argon spectrum in the range of 1200–2000 cm<Superscript>–1</Superscript>

Atomic argon spectrum in the range of 1200–2000 cm^–1 has been recorded by time-resolved Fourier transform spectroscopy. The lines have been identified using the oscillator strengths calculated by the quantum-defect method. Previously unknown energies of the 6h levels of Ar I have been found from the spectrum.     

Resistive switching behavior in a Ni–Ag<Subscript>2</Subscript>Se–Ni nanowire

Hysteretic resistive switching behavior in a silver selenide (Ag₂Se) nanowire, which had a diameter of about 200 nm and a length of about 10 μm, was studied using scanning probe microscopy. Electrical current measurements were carried out in a range from 0 to −10 V and in temperatures below and above the phase transition of Ag₂Se. ON/OFF switching times were measured with pulsed voltages. They displayed different characteristics at low and high temperatures. The results confirm that Ag₂Se nanowires have applications in nanoscale switching devices.     

Elastic properties of TeO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Ag<Subscript>2</Subscript>O glasses

A series of glasses [(TeO₂) _x (B₂O₃)_1−x ]_1−y [Ag₂O] _y with x = 70 and y = 10, 15, 20, 25 and 30 mol% were synthesised by rapid quenching. Longitudinal and shear ultrasonic velocity were measured at room temperature and at 5 MHz frequency. Elastic properties, Poisson's ratio, microhardness, softening temperature and Debye temperature have been calculated from the measured density and ultrasonic velocity at room temperature. The experimental results indicate that the elastic constants depend upon the composition of the glasses and the role of the Ag₂O inside the glass network is discussed. Estimated parameters based on Makishima–Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Comparison between the experimental elastic moduli data obtained in the study and the calculated theoretically by the mentioned above models has been discussed.     

Electrical switching in the MoO<Subscript>3</Subscript>–WO<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> and MoO<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

High field electrical switching on blown films of MoO₃(60%)–P₂O₅(40%), MoO₃(50%)–WO₃(10%)–P₂O₅(40%), and MoO₃(45%)–WO₃(15%)–P₂O₅(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses was observed. The important observation was that with the addition of WO₃ to binary MoO₃–P₂O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation between MoO₃ content and density which decreased with the increase of MoO₃ content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was explained by thermal (formation of crystalline filaments) and electronic models.     

Effect of mixed glass formers on the crystallization kinetics in AgI–Ag<Subscript>2</Subscript>O–V<Subscript>2</Subscript>O<Subscript>5</Subscript>–MoO<Subscript>3</Subscript> glassy superionic system

The crystallization and glass transition kinetics using differential scanning calorimetry (DSC) in 50AgI–33.33Ag₂O–16.67[(V₂O₅)_1−x –(MoO₃) _x ] superionic glassy system is discussed. Thermal stability of glass, studied using various criteria, does not vary significantly with glass former variation. However, the activation energies for structural relaxation (E _s) at glass transition temperature and crystallization (E _c) obtained using Moynihan and Kissinger, Matusita-Sakka formulations found to exhibit interesting trends with MoO₃ substitution in the glass matrix. It is noticed that the electrical conductivity (σ)–temperature (T) cycles obtained at a typical heating rate of 1 °C/min do exhibit significant thermal events. The conductivity after first heating cycle at room temperature is found to be increasing with MoO₃ content and maximum for x = 0.3 (~10⁻³ Ω⁻¹ cm⁻¹ at 30 °C) which is comparable to that of the host 50AgI–33.33Ag₂O–16.67V₂O₅ glassy system. The parameters obtained from σ–T plots and DSC scans do complement each other in a particular range of composition.     

Characterization and transport properties of 10BaO–xAg<Subscript>2</Subscript>O–(85-x)V<Subscript>2</Subscript>O<Subscript>5</Subscript>–5TeO<Subscript>2</Subscript> glass system

Silver-based quaternary glasses were prepared by splat quenching technique. X-ray diffraction and differential scanning calorimetry were done for confirming their amorphous nature. The conductivity of the glasses was measured in the frequency range from 1 Hz to 32 MHz from room temperature to 373 K. Conductivity data, which obeys the Arrhenius type behavior, shows minimum at 30 mol% Ag₂O, suggesting that the conductivity mechanisms are different above and below these two regions. The minimum in conductivity is accompanied by an inverse behavior of activation energy. Experimental data suggests that a polaron hopping mechanism operates in the electronically conducting domain of 20 ≤ × ≤ 30, and an interstitial pair mechanism operates in the ionically conducting domain of 35 ≤ × ≤ 55.     

Photoluminescence of Tb<Superscript>3+</Superscript> ions in barium–strontium–calcium titanate xerogels

Terbium-doped films of barium–strontium–calcium titanate with the perovskite phase were fabricated using the sol-gel method. Photoluminescence of trivalent terbium ions with a strong band at 543 nm was observed at 4.2 and 300 K for films fabricated by spin-on deposition on porous anodic alumina and annealed at 500 and 750°C. The possibility of using sol-gel synthesis of perovskites to investigate spontaneous emission of terbium and other lanthanides in photonic crystals with a tunable photonic band gap is discussed.     

A novel core–shell nanocomposite Ni–Ca@mSiO<Subscript>2</Subscript> for benzophenone selective hydrogenation

A novel core–shell nanocomposite Ni–Ca@mSiO₂ was first prepared by a modified Stöber method in this paper. It has a core–shell structure with Ni (about 8 nm in diameter) and Ca as the cores and mesoporous silica as the outer shell, as proven by the transmission electron microscopy. This nanocomposite exhibited good catalytic performance in the selective hydrogenation of benzophenone, with 96.1% conversion and 94.9% selectivity for benzhydrol under relatively mild reaction conditions. It was demonstrated that addition of small amounts of alkaline Ca can not only markedly improve the dispersion of the active species but also tune the acid–base property of this nanocomposite, resulting in the efficient suppression of benzhydrol dehydration to achieve a high selectivity. Furthermore, the core–shell nanocomposite Ni–Ca@mSiO₂ can be recycled four runs without appreciable loss of its initial activity, more stable than the traditional supported nanocatalyst Ni–Ca/mSiO₂. It was suggested that the outer mesoporous silica shell of Ni–Ca@mSiO₂ can prevent both the aggregation and the leaching of the active Ni species, accounting for its relatively good stability.

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Graphical abstract A magnetic core–shell nanocomposite Ni–Ca@mSiO₂ exhibited good activity, selectivity, and reusability in benzophenone selective hydrogenation.

     

Deep metastable eutectic nanometer-scale particles in the MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> system

Laboratory vapor phase condensation experiments systematically yield amorphous, homogeneous, nanoparticles with unique deep metastable eutectic compositions. They formed during the nucleation stage in rapidly cooling vapor systems. These nanoparticles evidence the complexity of the nucleation stage. Similar complex behavior may occur during the nucleation stage in quenched-melt laboratory experiments. Because of the bulk size of the quenched system many of such deep metastable eutectic nanodomains will anneal and adjust to local equilibrium but some will persist metastably depending on the time–temperature regime and melt/glass transformation.     

Haven Correlation Parameter for Diffusion of Fluorine in Superionic Conductors La1 – ySryF3 – y

Physics of the Solid State - The processes of electric charge transfer (conductivity) and mass transfer (diffusion) in La1&nbsp;‒&nbsp;ySryF3&nbsp;–&nbsp;y superionic...     

On simplifying ‘incremental remap’–based transport schemes

The flux-form incremental remapping transport scheme introduced by Dukowicz and Baumgardner [1] converts the transport problem into a remapping problem. This involves identifying overlap areas between quadrilateral flux-areas and regular square grid cells which is non-trivial and leads to some algorithm complexity. In the simpler swept area approach (originally introduced by Hirt et al. [2]) the search for overlap areas is eliminated even if the flux-areas overlap several regular grid cells. The resulting simplified scheme leads to a much simpler and robust algorithm.     

Sol–gel synthesis and characterization of Li<Subscript>2</Subscript>CO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite solid electrolytes

Composite solid electrolytes in the system (1???x)Li₂CO₃–xAl₂O₃, with x?=?0.0–0.5 (mole), were synthesized by a sol–gel method. The synthesis carried out at low temperature resulted in voluminous and fluffy products. The obtained materials were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy/energy-dispersive X-ray, Fourier transform infrared spectroscopy and AC impedance spectroscopy. Structural analysis of the samples showed an amorphous feature of Li₂CO₃ and traces of α-LiAlO₂, γ-LiAlO₂ and LiAl₅O₈. The prepared composite samples possess high ionic conductivities at 130–180 °C on account of the presence of lithium aluminates as well as the formation of a high concentration of an amorphous phase of Li₂CO₃ via this sol–gel preparative technique.     

Microwave dielectric properties of the 5.5Li<Subscript>2</Subscript>O–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>–7TiO<Subscript>2</Subscript> ceramics

A new Li₂O–Nb₂O₅–TiO₂ (LNT) ceramic with the Li₂O:Nb₂O₅:TiO₂ mole ratio of 5.5:1:7 was prepared by solid state reaction route. The phase and structure of the ceramic were characterized by X-ray diffraction and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied using a network analyzer. The microwave dielectric ceramic has low sintering temperature (∼1075°C) and good microwave dielectric properties of ε _r=42, Q×f=16900 GHz (5.75 GHz), and τ _f =63.7 ppm/°C. The addition of B₂O₃ can effectively lower the sintering temperature from 1075 to 875°C and does not induce degradation of the microwave dielectric properties. Obviously, the LNT ceramics can be applied to microwave low temperature-cofired ceramics (LTCC) devices.