Effect of normal phonon-phonon scattering on the mutual electron-phonon drag and kinetic phenomena in degenerate conductors

The effect of normal phonon-phonon scattering processes on momentum relaxation in a nonequilibrium electron-phonon system is considered. A system of rate equations for the electron and phonon distribution functions has been solved with the inclusion of mutual electron-phonon drag. The kinetic coefficients of conductors have been calculated in a linear approximation in the degeneracy parameter. The effect of normal phonon-phonon scattering processes on the electron-phonon drag and on the kinetic phenomena in conductors with degenerate carrier statistics is analyzed.     

Coulomb drag between one-dimensional conductors

We have analyzed Coulomb drag between currents of interacting electrons in two parallel one-dimensional conductors of finite length L attached to external reservoirs. For strong coupling, the relative fluctuations of electron density in the conductors acquire energy gap M. At energies larger than gamma = constxv(-)exp(-LM/v(-))/L+gamma(+), where gamma(+) is the impurity scattering rate, and, for L>v(-)/M, where v(-) is the fluctuation velocity, the gap leads to an "ideal" drag with almost equal currents in the conductors. At low energies the drag is suppressed by coherent instanton tunneling, and the zero-temperature transconductance vanishes, indicating the Fermi-liquid behavior.     

Drag effect and topological complexes in strongly interacting two-component lattice superfluids

The mutual drag in strongly interacting two-component superfluids in optical lattices is discussed. Two competing drag mechanisms are the vacancy-assisted motion and proximity to a quasimolecular state. In a case of strong drag, the lowest energy topological excitation (vortex or persistent current) can consist of several circulation quanta. In the SQUID-type geometry, the circulation can become fractional. We present both the mean field and Monte Carlo results. The drag effects in optical lattices are drastically different from the Galilean-invariant Andreev-Bashkin effect in liquid helium.     

Phase transitions and dynamics of superionic conductors

A Hamiltonian is constructed for superionic conductors taking into account the mutual interactions and transports of the mobile ions, and their interactions with the phonons of the cage. Under special conditions we recover the phenomenological results of Rice et al. and Huberman in regard to phase transitions. Two transition points are shown to be possible in the presence of the mutual interactions of cations (as observed in RbAg₄I₅ and CuBr). Structural phase transitions involving the cage when exist are found to occur at the same temperature at which the conductivity becomes critical, in agreement with experiments. Dynamical aspects of our Hamiltonian are also discussed. The collective modes of the phonon-cation system are calculated and used to explain the abrupt disappearance of certain modes above the critical temperature as observed in the Raman spectra of RbAg₄I₅, KAg₄I₅ and AgI. Our theory does contain the possibility that there is no soft mode with nonzero frequency, in accordance with the existing experimental situation. Our Hamiltonian is compared to others. The similarities between superionic conductors and other systems (Hubbard model, ferroelectrics, Jahn-Teller systems, molecular crystals) are emphasized.     

Electron-phonon entrainment, thermodynamic effects, and the thermal conductivity of degenerate conductors

A method is proposed for calculating the kinetic coefficients of degenerate conductors that takes into account in a self-consistent way the mutual influence of the nonequilibrium state of the electron and phonon subsystems. The calculated expressions for the kinetic coefficients satisfy Onsager symmetry relations. The influence of the nonequilibrium character of the electron-phonon subsystem on the electrical conductivity, thermal voltage, and electronic thermal conductivity is analyzed. Fiz. Tverd. Tela (St. Petersburg) 41, 1753–1762 (October 1999)     

Electron-phonon drag in degenerate conductors in a magnetic field

Mutual drag of electrons and phonons in degenerate conductors in classical magnetic fields is considered. It is shown that the coupled kinetic equations for nonequilibrium electron and phonon distribution functions can be transformed into a system of Volterra’s inhomogeneous integral equations. A solution is found to the system of integral equations with inclusion of all terms yielding contributions linear in the degeneracy parameter. An analysis is made of the effect of a magnetic field on momentum relaxation in an electron-phonon system.     

Sliding friction with polymer brushes

Using high-resolution shear force measurements, we examine in detail the frictional drag between rubbing surfaces bearing end-tethered polymeric surfactants (brushes). The drag attains a maximum on initial motion, attributed to elastic stretching of the chains, which falls by a cascade of relaxations to a value characteristic of kinetic friction. This has a very weak velocity dependence, attributed to chain moieties dragging within a self-regulating, mutual interpenetration zone. When sliding stops, the shear stress across the polymer layers decays logarithmically with time, consistent with the relaxation of a network of dangling ends.     

Filament architectures in AC conductors: the influence of intergrowths

Filament isolation is an extremely important factor in multi-filamentary conductors, and attempts have been made to achieve this by incorporating a resistive oxide sheath around individual filaments. However, filament-bridging intergrowths have been observed in conductors with and without the resistive sheath. We present magnetisation results on BSCCO-2223/Ag conductors with different filament configurations, and analyse the data taking into account the effects of magnetic coupling between filaments. All samples studied display some degree of filament bridging.     

Determination of the magnetic field of a bifilar lead by means of the method of images

The method of the images has been applied to determine the magnetic field of a bifilar lead. Arbitrary dimensions of the conductors have been considered. The permeability of one of conductors has been assumed to be different from the free-space permeability.     

Recent Developments in Oxide-Based Ionic Conductors: Bulk Materials,Nanoionics, and Their Memory Applications

Oxide-based ionic conductors have attracted tremendous research interests due to their wide applications in energy storage and conversion devices, such as photovoltaics, fuel cells, batteries, and supercapacitors. Extensive efforts have been undertaken to improve the ionic conductivity of existing materials along with the development of novel conductors. The recent advance of ionic conductors in nanoscale demonstrated their ultra–high ionic conductivity for the promising applications in energy sector. In this work, recent progresses of conventional oxide conductors and the development of novel conductors are reviewed in details. The strategy to exploit the nanoionics of enhancing the ionic conductivity is discussed. Furthermore, the novel applications of nanoionics for the resistive switching memories are summarized.     

Transport and AC loss properties of the repaired multifilamentary REBCO superconducting tapes

For near-future applications of REBa₂Cu₃O₇ (REBCO) coated conductors to electric power cables, transformers and Superconducting Magnetic Energy Storage (SMES), the long taped wires with high performance in the transport properties have been designed and fabricated. Moreover, in order to drastically reduce AC losses in perpendicular field configuration, advanced multifilament YBCO coated conductors (MFYCCs) fabricated with technique of a laser scribing process have been also developed. In the present study, from engineering viewpoints to utilize such advanced conductors, we evaluated the transport and AC loss properties of short MFYCCs with a repaired part or a joint by a diffusion joint technique with the saddle-shaped pickup coil method.     

A model for the heat of transport in ionic conductors

The ion flow caused by a temperature gradient originates the ionic thermopower which is quantified by the heat of transport. Experimentally, it is known that in superionic conductors, the heat of transport Q is nearly equal to the activation energy for ion transport E_a. In the present paper, a model for the heat of transport in ionic conductors has been proposed based on a lattice dynamical theory of diffusion. We have shown that the relationship between Q and E_a is determined by the participation degree of different phonon modes, in particular the short wavelength phonons to the atomic jump processes. The implication of this finding to the transport properties of superionic conductors has been discussed, and it is suggested that the degree of the collective motion in ionic conductors increases with the increase in Q/E_a. The model predicts that good ionic conductors will show large value of Q/E_a. The importance of the acoustic phonons in the ion transport processes has been also pointed out.     

Electric fields in compact clusters of parallel current channels

The electric field in compact clusters of parallel current channels is calculated in the model of a bundle of long parallel cylindrical conductors. It is shown that, because of the mutual neutralization of the fields of individual microchannels, the maximal radial electric field in a compact cluster of microchannels can be lower than the critical field needed for ionization multiplication and channel expansion. This explains the existence of groups of microchannels (less than 10 μm in radius) in high-voltage nanosecond diffuse and spark discharges.     

Forcing inertial Brownian motors: Efficiency and negative differential mobility

The noise-assisted, directed transport in a one-dimensional dissipative, inertial Brownian motor of the rocking type that is exposed to an external bias is investigated. We demonstrate that the velocity–load characteristics is distinctly non-monotonic, possessing regimes with a negative differential mobility. In addition, we evaluate several possible efficiency quantifiers which are compared among each other. These quantifiers characterize the mutual interplay between the viscous drag and the external load differently, weighing the inherent rectification features from different physical perspectives.     

Atomistic simulation of the motion of dislocations in metals under phonon drag conditions

The mobility of dislocations in the over-barrier motion in different metals (Al, Cu, Fe, Mo) has been investigated using the molecular dynamics method. The phonon drag coefficients have been calculated as a function of the pressure and temperature. The results obtained are in good agreement with the experimental data and theoretical estimates. For face-centered cubic metals, the main mechanism of dislocation drag is the phonon scattering. For body-centered cubic metals, the contribution of the radiation friction becomes significant at room temperature. It has been found that there is a correlation between the temperature dependences of the phonon drag coefficient and the lattice constant. The dependences of the phonon drag coefficient on the pressure have been calculated. In contrast to the other metals, iron is characterized by a sharp increase in the phonon drag coefficient with an increase in the pressure at low temperatures due to the α-∈ phase transition.     

Calculation of the drag and heat transfer from a sphere in the gas flow in a cylindrical channel

A numerical experiment on the simulation of heat transfer from a sphere to a gas flow in a cylindrical channel in the Stokes and transient flow regimes has been described. Radial and axial profiles of the gas temperature and the dependences of drag coefficient C_d of the body and Nusselt number Nu on Reynolds number Re have been calculated and analyzed. The problem of the influence of the early drag crisis for a sphere on its heat transfer to the gas flow has been considered. The estimation of this phenomenon has shown that the early drag crisis of the sphere in a strongly turbulent flow causes a reduction in heat transfer from the sphere to the gas by three to six times (in approximately the same proportion as for its drag coefficient).     

Features of the electron-photon drag effect in a spiral ribbon in the external magnetic field

The features of the photon drag effect in a spiral two-dimensional ribbon, which are associated with an asymmetric electron energy spectrum in a longitudinal magnetic field, have been studied theoretically. The effect of the anisotropic transfer of the photon momentum to the electron system in a spectral dependence of the photon drag current density has been revealed.     

椭圆柱坐标下等值坐标带电导体柱的电势与电场分布

利用椭圆柱坐标求解共焦共轴带电导体双椭圆柱和双曲柱电势和电场的分布,并对一些特例作了讨论.     

Investigation of materials at microwave frequencies using microstrip sensors

Microstrip sensors are developed for measurements of dielectric and magnetic characteristics of materials in a wide range of frequencies 20–10,000 MHz. Their operation is based on both conventional resonance measurements techniques and an original method for measuring position and depth of the attenuation pole that is a point of mutual compensation of the inductive and capacitive interaction of microstrip conductors. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 46–53, September, 2006.     

The positivity and other properties of the matrix of capacitance: Physical and mathematical implications

We prove that the matrix of capacitance in electrostatics is a positive-singular matrix with a non-degenerate null eigenvalue. We explore the physical implications of this fact, and study the physical meaning of the eigenvalue problem for such a matrix. Many properties are easily visualized by constructing a “potential space” isomorphic to the euclidean space. The problem of minimizing the internal energy of a system of conductors under constraints is considered, and an equivalent capacitance for an arbitrary number of conductors is obtained. Moreover, some properties of systems of conductors in successive embedding are examined. Finally, we discuss some issues concerning the gauge invariance of the formulation.