Oscillatory Dependence Research Articles

Resonance interaction energy between two entangled atoms in a photonic bandgap environment

We consider the resonance interaction energy between two identical entangled atoms, where one is in the excited state and the other in the ground state. They interact with the quantum electromagnetic field in the vacuum state and are placed in a photonic-bandgap environment with a dispersion relation quadratic near the gap edge and linear for low frequencies, while the atomic transition frequency is assumed to be inside the photonic gap and near its lower edge. This problem is strictly related to the coherent resonant energy transfer between atoms in external environments. The analysis involves both an isotropic three-dimensional model and the one-dimensional case. The resonance interaction asymptotically decays faster with distance compared to the free-space case, specifically as 1/r2 compared to the 1/r free-space dependence in the three-dimensional case, and as 1/r compared to the oscillatory dependence in free space for the one-dimensional case. Nonetheless, the interaction energy remains significant and much stronger than dispersion interactions between atoms. On the other hand, spontaneous emission is strongly suppressed by the environment and the correlated state is thus preserved by the spontaneous-decay decoherence effects. We conclude that our configuration is suitable for observing the elusive quantum resonance interaction between entangled atoms.

Near-field three-terminal thermoelectric heat engine

We propose a near-field inelastic thermoelectric heat engine where quantum-dots are used to effectively rectify the charge flow of photo-carriers. The device converts near-field heat radiation into useful electrical power. Heat absorption and inelastic transport can be enhanced by introducing two continuous spectra separated by an energy gap. The thermoelectric transport properties of the heat engine are studied in the linear-response regime. Using a small band-gap semiconductor as the absorption material, we show that the device achieves very large thermopower and thermoelectric figure-of-merit, as well as considerable power-factor. By analyzing thermal-photo-carrier generation and conduction, we reveal that the Seebeck coefficient and the figure of merit have oscillatory dependence on the thickness of the vacuum gap. Meanwhile, the power-factor, the charge and thermal conductivity are significantly improved by near-field radiation. Conditions and guiding principles for powerful and efficient thermoelectric heat engines are discussed in details.

Current oscillations in Schottky-barrier CNTFET: towards resonant tunneling device operation

In this work, it has been shown that current oscillations could be enhanced in Schottky-barrier carbon nanotube FET (SB-CNFET) particularly at the low drain voltage and small channel lengths. This oscillatory dependence on the gate voltage brings out negative differential transconductance regions. We have simulated the SB-CNTFET using a 2D quantum simulator by solving NEGF and Poisson’s equation self-consistently. A parabolic potential well profile between double barriers is formed along the transport direction of the channel which is responsible for these oscillations. Key factors that affect the current oscillations are thoroughly investigated such as drain voltage, channel length, CNT diameter, the dielectric constant of the gate oxide and temperature. The results of this work pave a way to shed light on the feasibility and enhancement of SB-CNTFET as a resonant tunneling device.

Oscillatory structure–property correlation in azelate polyols and thermoplastic polyurethanes

ABSTRACTAzelate polyols of 2000 g mol−1 have been successfully prepared via esterification of renewable azelaic acid with linear diols containing different number of CH2 repeating units. Structure–property correlation of the azelate polyols had been evaluated in thermoplastic polyurethanes (TPUs). TPUs based on azelate polyols of longer chained linear diols with >4 CH2 repeat units retained higher degrees of crystallinity associated with the polyol soft segment. The ratio of hydrogen bonded urethane in the hard segment to free urethane phase mixed with the soft segment in the TPUs showed a complex oscillating dependence with increased number of CH2 repeating unit in the linear diols of azelate polyols. Correspondingly, static and dynamic properties of TPUs also showed the oscillatory dependence, whereby dynamic properties maximized with odd number of CH2 repeating unit and material strength maximized with even number of CH2 repeating unit. The results therefore can be used as guide to select appropriate azelate polyols to target specific TPU performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46258.

Heat of adsorption, adsorption stress, and optimal storage of methane in slit and cylindrical carbon pores predicted by classical density functional theory.

Temperature, pressure and pore-size dependences of the heat of adsorption, adsorption stress, and adsorption capacity of methane in simple models of slit and cylindrical carbon pores are studied using classical density functional theory (CDFT) and grand-canonical Monte-Carlo (MC) simulation. Studied properties depend nontrivially on the bulk pressure and the size of the pores. Heat of adsorption increases with loading, but only for sufficiently narrow pores. While the increase is advantageous for gas storage applications, it is less significant for cylindrical pores than for slits. Adsorption stress and the average adsorbed fluid density show oscillatory dependence on the pore size and increase with bulk pressure. Slit pores exhibit larger amplitude of oscillations of the normal adsorption stress with pore size increase than cylindrical pores. However, the increase of the magnitude of the adsorption stress with bulk pressure increase is more significant for cylindrical than for slit pores. Adsorption stress appears to be negative for a wide range of pore sizes and external conditions. The pore size dependence of the average delivered density of the gas is analyzed and the optimal pore sizes for storage applications are estimated. The optimal width of slit pore appears to be almost independent of storage pressure at room temperature and pressures above 10 bar. Similarly to the case of slit pores, the optimal radius of cylindrical pores does not exhibit much dependence on the storage pressure above 15 bar. Both optimal width and optimal radii of slit and cylindrical pores increase as the temperature decreases. A comparison of the results of CDFT theory and MC simulations reveals subtle but important differences in the underlying fluid models employed by the approaches. The differences in the high-pressure behaviour between the hard-sphere 2-Yukawa and Lennard-Jones models of methane, employed by the CDFT and MC approaches, respectively, result in an overestimation of the heat of adsorption by the CDFT theory at higher loadings. However, both adsorption stress and adsorption capacity appear to be much less sensitive to the differences between the models and demonstrate excellent agreement between the theory and the computer experiment.

APPLIED INFORMATICS MODEL ОF KINETICS ACCOUNTING OF CYBERNETIC THREATS IN NPP PHYSICAL PROTECTION SYSTEM

Context. The topical approaches to preventive estimations and mathematical modeling of cyber attacks processes and supply of external technological informational threats were considered, which may be directed on the physical security system of modern nuclear power plant units. Objective – is an adaptation of known mathematical models of cyber attacks kinetics for use in the system of information security and physical protection of nuclear power plants to modern and foreseeable conditions. Method. The method of model dependencies adaptation was proposed, which reflects the kinetics of cyberattacks to the modern operating conditions of protected nuclear facilities was proposed. To improve the model dependencies it was proposed to modify the classic Ferhulst function and, in mathematical modeling of cyber attacks on nuclear power facilities, to use the appropriate transformation of the logistic curve, which has distinctive feature of a well-defined maximum. Results. It was predicted that the model dependence of flow external to NPP cyber threats can be characterized by the alternation of maxima and minima, which indicates the possibility of an oscillatory character of the developing process. Also was put forward and substantiated the hypothesis that the system of physical and, in particular, cybernetic, NPP protection can be characterized by a time lag that in view of possible oscillatory character of information threats admissions process creates the preconditions for the development of oscillatory instability. The results obtained in the research are of applied nature, they can be used to carry out large-scale experiments and forecasting parameters of possible cyber threats aimed at the NPP for the purpose of pre-emption and preventive maintenance of information safety of modern nuclear energy technologies. Conclusions. Recommended for use model dependences were first adapted to the conditions of operating conditions of nuclear powerfacilities, take into account the factors to counter threats and circumstances associated with a specific time delay. It was shown for the first time that there is an opportunity both extreme and oscillatory dependence nature of the cyber attacks intensity, which are focused on software and hardware system of NPP information safety. The new approach allows to assume the reality of the unstable oscillation process in the “attack – defense” system and provides an opportunity of preventive assessment of the stability stocks. The practical significance lies in the fact that the results allow to realistically assess the time of onset of expected cyber attacks current dependence changes and to use this knowledge for organizational and technical preparation of remedies and early anticipation of IT-threats.

Ultrasonic bandgaps and interlaminar interface echoes of composite laminates: Analysis and experiments

Increasing applications of carbon fiber reinforced plastics (CFRP) in aerospace industry highlight the importance of nondestructive methods to characterize their mechanical properties as well as defect concentrations. In CFRP laminate structures, thin resin layers, typically of a few micron thickness, are present between plies. Their spatially periodic nature causes bandgaps for ultrasonic waves having wavelengths comparable to the ply thickness. Features of the reflection and transmission spectra of ultrasonic waves including such bandgaps can be utilized for nondestructive characterization of CFRP laminates. In particular, the oscillatory frequency dependence of the reflection or transmission spectra of ultrasonic waves near the band gaps can be used to identify the equivalent stiffnesses of interlaminar interfaces. These interfacial stiffnesses contain rich information of the mechanical soundness of the interlaminar interfaces which are otherwise difficult to evaluate with traditional ultrasonic methods working in relatively low frequencies. The evidence of ultrasonic bandgaps of CFRP laminates can also be observed as long-standing signals following the surface echo in the temporal reflection waveforms of CFRP laminates (interlaminar interface echoes). In this presentation, the physical phenomena behind the ultrasonic bandgaps and interlaminar interface echoes of CFRP laminates are discussed together with their applications to nondestructive characterization of these materials.

Plasmonic Interference in Superstructured Metal Photonic Crystals

Surface plasma waves (SPWs) excited by illumination of 2-dimensional superstructured metal photonic crystals (SMPCs) are investigated with extraordinary optical transmission (EOT). An m × m lattice of holes (m = 3 with the period p of 3 μm) fabricated in an Au film atop a GaAs substrate (refractive index nd), referred to as a basis plasmonic antenna (BPA), forms an SMPC that consists of 24 × 24 BPAs with varying spacing between BPAs, d. Two categories of d are examined: κ = d/p = i (i an integer), where SPWs generated at each BPA interfere constructively and κ ≠ i (<1), where the interference leads to drastic changes in the EOT. In the first category, the EOT associated with the fundamental SPW wavelength, T1, decreases with increasing κ, but has an almost invariant peak wavelength, λ1, at ∼10.1 μm (≅ndp), as expected. In the second category, however, the λ1 for the dominant EOT peak clearly shows a red-shift to ∼12 μm with T1 reduced to ∼0 at κ = 0.5, and T1 has a damped oscillatory dependence on κ. The ...

Oscillatory dependence of tunneling conductance on the barrier thickness

Oscillatory dependence of tunneling conductance on the barrier thickness

Electrical degradation on DC and RF characteristics of short channel AlGaN/GaN-on-Si hemt with highly doped carbon buffer

Oscillatory dependence of tunneling conductance on the barrier thickness is investigated theoretically for the metal/insulator/metal junctions. The tunneling transmission is expressed with the reflection and the transmission amplitudes of each separated metal/insulator interface and the wavevectors inside the barrier. An analytical formula is obtained for the tunneling conductance. The oscillatory behavior of the tunneling conductance is possible with the complex band structure of the insulator. The oscillation period is determined not directly from the real part of the complex wavevector in the insulator, but from the extremal complex spanning vector of the complex Fermi surface of the insulator.

Behavior of a supercooled chalcogenide liquid in the non-Newtonian regime under steady vs. oscillatory shear

The steady and oscillatory shear rate dependence of viscosity of a supercooled chalcogenide liquid of composition As10Se90 is measured at Newtonian viscosities ranging between 103 and 107 Pa s using capillary and parallel plate rheometry. The liquid displays strong violation of the Cox-Merz rule in the non-Newtonian regime where the viscosity under steady shear is nearly an order of magnitude lower than that under oscillatory shear. This behavior is argued to be related to the emergence of unusually large (6-8 nm) cooperatively rearranging regions with long relaxation times in the liquid that result from significant structural rearrangements under steady shear.

Surface current at non-magnetic metal/ferromagnetic insulator interface due to Rashba spin-orbit interaction

We theoretically investigate a new mechanism of interfacial current in a two-layer system consisting of a magnetic insulator and an adjacent non-magnetic metal. The mechanism is based on Rashba spin-orbit interaction in the metal layer near the interface where the magnetic insulator induces non-zero magnetization. The rotation of the magnetization of the magnetic insulator induces the alternating interfacial current in the non-magnetic metal. Coordinate and time dependencies of the current and induced magnetization in the non-magnetic layer are calculated using quasi-energy approach assuming ballistic conductivity in non-magnetic metal. It is found that the current displays sizable magnitude within the metal layer over a distance which significantly exceeds a region with non-zero spin-orbit interaction. Both the current and the spin density induced in the metal layer demonstrate oscillatory dependence as a function of the distance from the interface due to the interference of the incoming and reflected waves.

Motion and Switching of Dual-Vortex Cores in Elliptical Permalloy Nanodisk Stimulated by a Gaussian Magnetic Field Pulse

Magnetic nanostructures have potential applications in ultrahigh-density magnetic storage. In this paper, the dynamics of the dual magnetic vortices in elliptical Permalloy nanodisk are investigated using micromagnetic modeling. Under the stimulation of the short-axis ( $y$ -axis) Gaussian field pulse and long-axis ( $x$ -axis) constant field, the equilibrium positions of dual-vortex cores can be driven away from the initial positions. The displacement in the $y$ -direction is proportional to the magnitude of the $x$ -axis constant field. The displacement in the $x$ -direction exhibit periodic reliance on the pulsewidth of the $y$ -axis Gaussian field pulse. The threshold value of pulse strength for dual-vortex motion increases with the magnitude of the $x$ -axis constant field. The mechanism of polarity and chirality switching in dual-vortex cores are studied through analyzing the trajectories of vortex cores in the annihilation and nucleation processes. The switching of polarity exhibits an oscillatory dependence on the pulsewidth and strength. The minimum pulse strength required for chirality switching is 120 mT, while the corresponding pulsewidth is influenced by the $x$ -axis constant field. This paper provides insights on the magnetization dynamics of nanostructures containing dual vortices subject to external excitations.

Atomic structure study of the pyrochloreYb2Ti2O7and its relationship with low-temperature magnetic order

Exchange interactions with itinerant electrons are known to act as a relaxation mechanism for individual local spins. The same exchange interactions are also known to induce the so called RKKY indirect exchange interaction between two otherwise decoupled local spins. Here we show that both the spin relaxation and the RKKY coupling can be seen as the dissipative and reactive response to the coupling of the local spins with the itinerant electrons. We thereby predict that the spin relaxation rates of magnetic nanostructures of exchanged coupled local spins, such as as nanoengineered spin chains, have an oscillatory dependence on $k_F d$ , where $k_F$ is the Fermi wave length and $d$ is the inter-spin distance, very much like the celebrated oscillations in the RKKY interaction. We demonstrate that both $T_1$ and $T_2$ can be enhanced or suppressed, compared to the single spin limit, depending on the interplay between the Fermi surface and the nanostructure geometrical arrangement. Our results open a route to engineer spin relaxation and decoherence in atomically designed spin structures.

RKKY oscillations in the spin relaxation rates of atomic-scale nanomagnets

Exchange interactions with itinerant electrons are known to act as a relaxation mechanism for individual local spins. The same exchange interactions induce the so-called RKKY indirect exchange interaction between two otherwise decoupled local spins. Here, we show that both the spin relaxation and the RKKY coupling can be seen as the dissipative and reactive response to the coupling of the local spins with the itinerant electrons. We thereby predict that the spin relaxation rates of magnetic nanostructures of exchanged coupled local spins, such as nanoengineered spin chains, have an oscillatory dependence on ${k}_{F}d$, where ${k}_{F}$ is the Fermi wave number and $d$ is the interspin distance, very much like the celebrated oscillations in the RKKY interaction. We demonstrate that both ${T}_{1}$ and ${T}_{2}$ can be enhanced or suppressed, compared to the single-spin limit, depending on the interplay between the Fermi surface and the nanostructure geometrical arrangement. Our results open a route to engineer spin relaxation and decoherence in atomically designed spin structures.

Quantum particle interacting with a metallic particle: Spectra from quantum Langevin theory

The effect of a nearby metallic particle on the quantum optical properties of a quantum particle in the four-level double Raman configuration is studied using the quantum Langevin approach. We obtain analytical expressions for the correlated quantum fields of Stokes and anti-Stokes photons emitted from the system and perform analysis on how the interparticle distance, the direction of observation or detection, the strengths of controllable laser fields, the presence of surface plasmon resonance, and the number density of the quantum particle affect the quantum spectra of the Stokes and anti-Stokes fields. We explore the physics behind the quantum-particle\char21{}metallic-nanoparticle interaction within the dipole approximation, that is, when the interparticle distance is much larger than the sizes of the particles. Our results show the dependence of the spectra on the interparticle distance in the form of oscillatory behavior with damping as the interparticle distance increases. At weaker laser fields the enhancement of quantum fields which manifests itself in the form of a Fano dip in the central peak of the spectra becomes significant. Also, the quantum-particle\char21{}metallic-nanoparticle coupling, which is affected by the size of the metallic nanoparticle and the number density of the quantum particle, changes the angular dependence of the spectra by breaking the angular rotational symmetry. In the presence of surface plasmon resonance the oscillatory dependence of the spectra on the interparticle distance and angles of observation becomes even stronger due to the plasmonic enhancement effect.

Near-equilibrium measurement of quantum size effects using Kelvin probe force microscopy.

In nano-structures such as thin films electron confinement results in the quantization of energy levels in the direction perpendicular to the film. The discretization of the energy levels leads to the oscillatory dependence of many properties on the film thickness due to quantum size effects. Pb on Si(111) is a specially interesting system because a particular relationship between the Pb atomic layer thickness and its Fermi wavelength leads to a periodicity of the oscillation of two atomic layers. Here, we demonstrate how the combination of scanning force microscopy (SFM) and Kelvin probe force microscopy (KPFM) provides a reliable method to monitor the quantum oscillations in the work function of Pb ultra-thin film nano-structures on Si(111). Unlike other techniques, with SFM/KPFM we directly address single Pb islands, determine their height while suppressing the influence of electrostatic forces, and, in addition, simultaneously evaluate their local work function by measurements close to equilibrium, without current-dependent and non-equilibrium effects. Our results evidence even-odd oscillations in the work function as a function of the film thickness that decay linearly with the film thickness, proving that this method provides direct and precise information on the quantum states.

Sorting ring polymers by knot type with modulated nanochannels.

In this theoretical study we discuss a novel method for sorting ring polymers according to their topological, knotted state. The proposed approach harnesses the rich dynamical behaviour of polymers confined inside spatially-modulated nanochannels. The longitudinal mobility of the rings is shown to have two key properties that are ideally suited for knot sorting. First, at fixed topology, the mobility has an intriguing oscillatory dependence on chain length. Second, the mobility ranking of different knot types is inverted upon increasing the chain length. We show that this complex interplay of channel geometry, chain length and topology can be rationalised within a simple theoretical framework based on Fick-Jacobs's diffusive theory. The results and the interpretative scheme ought to be useful for designing microfluidic devices with optimal topological sorting capabilities.

Confinement effects on phase separation of a polyelectrolyte solution

Formulating an analytical theory, we study phase separation of a polyelectrolyte solution under poor solvent condition confined in three types of finite geometric spaces: slab, cylinder, and sphere. Divided by a Lifshitz line, bulk polyelectrolyte solution undergoes either micro- or macro-phase separation. Confinement effects for both scenarios are studied. Composition fluctuations inducing phase separation are classified in terms of eigenmodes of the inverse structure factor operator in the corresponding geometric spaces. Tracking each eigenmode, the instability lines under confinement effects are derived in closed forms. For the confined microphase separation, we find a decaying oscillatory dependence of the spinodal point on the confinement size, which represents the commensurability between the finite period of the soft mode and the confining boundary size. For the confined macrophase separation, a typical mean-field finite size scaling of the Ising universality class is observed under the strong screening condition.

Impurity effects on ionic-liquid-based supercapacitors

ABSTRACTSmall amounts of an impurity may affect the key properties of an ionic liquid and such effects can be dramatically amplified when the electrolyte is under confinement. Here the classical density functional theory is employed to investigate the impurity effects on the microscopic structure and the performance of ionic-liquid-based electrical double-layer capacitors, also known as supercapacitors. Using a primitive model for ionic species, we study the effects of an impurity on the double layer structure and the integral capacitance of a room temperature ionic liquid in model electrode pores and find that an impurity strongly binding to the surface of a porous electrode can significantly alter the electric double layer structure and dampen the oscillatory dependence of the capacitance with the pore size of the electrode. Meanwhile, a strong affinity of the impurity with the ionic species affects the dependence of the integral capacitance on the pore size. Up to 30% increase in the integral capacitance can be achieved even at a very low impurity bulk concentration. By comparing with an ionic liquid mixture containing modified ionic species, we find that the cooperative effect of the bounded impurities is mainly responsible for the significant enhancement of the supercapacitor performance.