Spin singlet-triplet states of superfluid Fermi liquids in the presence of strong magnetic fields

The unitary singlet-triplet states of superfluid Fermi liquids are investigated in the presence of strong magnetic fields. The static spin susceptibility is calculated in the limith 0 in the framework of the weak coupling approximation. It is predicted that BS (a mixture of the Balian- Werthamer anisotropic state andD-wave singlet state) and 2DS (a mixture of the planar 2D state andD-wave singlet state) spin singlet-triplet states become stable at some temperatures and magnetic fields.     

The spin diffusion in normal and superfluid Fermi liquids

Spin diffusion in paramagnetic spin systems is a dissipative process which acts so as to remove all spatial variation of the magnetization. In normal and superfluid Fermi liquids its physical origin lies in the nonconservation property of the macroscopic magnetization current associated with the thermal excitations, the Landau and Bogoliubov quasiparticles, respectively. In the hydrodynamic limit this dissipative process manifests itself in a constitutive relation connecting the decaying magnetization current with gradients in the magnetization density via a coefficient of spin diffusion. Exchange contributions to the quasiparticle interaction introduce, in addition, reactive processes, which can be associated with a rotation of the quasiparticle spin current about the direction of the spin polarization. This so-called spin current rotation—or Leggett-Rice effect—leads to nonhydrodynamic behavior of the spin diffusion whenever the exchange frequency becomes comparable to the inverse spin current relaxation time. In this article I would like to review our current understanding of diffusional spin transport, as influenced by nonhydrodynamic effects, in normal and superfluid Fermi systems.Dedicated to Ludwig Tewordt on the occasion of his 65th birthday.     

Nonlinear eddy current effects in ferromagnetic materials in the presence of DC magnetic fields

Eddy current effects in nonlinear ferromagnetic materials in the presence of a supplementary DC magnetic field are analyzed. The analysis is for a one-dimensional configuration, a semi-infinite plate magnetized homogeneously in a direction parallel to its surface. The nonlinear magnetization characteristic of the ferromagnetic plate material is assumed to be of a step-function form. Solutions of the electric field intensity on the plate surface, the penetration depth of eddy currents in the plate, the eddy current losses, and surface impedance in the presence of a DC magnetic field are obtained. A connection is found between the values obtained in simultaneous DC and AC magnetization conditions and the values obtained in the case of only AC magnetic field excitation.<>     

Mechanisms for electric and magnetic fields effects on biological cells

The application of electric and magnetic fields to biological systems can lead to changes that occur through a variety of physical mechanisms. These include changes in the ionic and molecular currents, changes in temperature due to heating, the lifetimes of free radicals, and the orientation of molecules. The importance of these mechanisms is a function of the biological system, the applied frequency, amplitude, and the length of exposure. These physical mechanisms, in turn, lead to changes in chemical reaction rates, molecular bindings to membranes, signaling between cells, and changes in the biology by way of changes in growth rates and cell functions, etc. In this paper, some ways in which measurements can be made to help sort out the physics leading to some of observed biological changes are described.     

Linear and nonlinear optical properties in an asymmetric double quantum well under intense laser field: Effects of applied electric and magnetic fields

In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting.     

Analytical investigation of eddy currents in nonlinear ferromagnetic media for weak magnetic fields

Electromagnetic field diffusion into a nonlinear ferromagnetic conducting half-space is analytically investigated for weak magnetic fields. For these fields a "nth power" approximation for magnetization curves is used. The exact analytical solutions to the non-linear partial differential equations of electromagnetic field theory are found for circular polarization of incident waves. The case of noncircular polarization is treated as a perturbation of circular polarization. Linear equations for perturbations are then derived and their analytical solutions are found. The analytical theory is illustrated by the computational results for surface impedances and third harmonics of electromagnetic fields.     

Zero-temperature attenuation and transverse spin dynamics in Fermi liquids. I. Generalized Landau theory

This is the first in a series of papers on a consistent microscopic theory of transverse dynamics in spin-polarized or binary Fermi liquids. We start from exact microscopic equations in Green's functions at zero temperatures and consider slightly inhomogeneous perturbations. The transverse dynamics is described by an integral equation in a 4D momentum space with inevitable spatial and temporal non-localities. This equation can be reduced only to a set of two coupled equations for partial transverse densities corresponding to independent contributions to a transverse magnetic moment from transverse components of slightly tilted up and down spins. It is shown that, in contrast to previous phenomenological theories of polarized Fermi liquids, these equations reduce to a single Landau-like kinetic equation only in cases of low polarization or density. This implies the existence of two different sorts of (attenuating) transverse quasi-particles. The molecular field (an analog of a Landau function) has a form of a 4-component non-local operator. This interaction operator is expressed via the off-diagonal component of the exact irreducible vertex with the help of some integral equation, and cannot be given, as it is usually assumed, as any limit of the full vertex. The proper Landau-like phenomenological approach corresponding to our exact microscopic equations, should operate with two types of attenuating transverse quasi-particles each oscillating between its Fermi surface and some other 3D surface in a 4D momentum space. The dephasing of inhomogeneous precession between two different types of dressed transverse quasi-particles leads to an inhomogeneous broadening which manifests itself as a peculiar zero-temperature relaxation.     

Hydrodynamic effects in water media in electric and magnetic fields

Journal of Engineering Physics and Thermophysics -     

The metal-dielectric transition in semimetals in extremely high magnetic fields. I

An analysis is given of a model of a semimetal with isotropic electron and hole spectra, separated in momentum space. The applied magnetic field is assumed to be strong enough to ensure that only one quantum level participates in each spectrum. The overlapping of levels is such that the Fermi energy is greater than the binding energy of the particle pairs. Weak point interaction is assumed to operate between the particles, which is valid for fields and dielectric constants that are not too high. The sign of the interaction can be arbitrary. Since the analysis is concerned with spinless fermions (degeneracy removed by the field), the system exhibits interactions between electrons and holes, but there is no interaction between particles of the same kind. It is shown that Cooper pairing of particles with the same charge is absent, but electron-hole excitons are formed, i.e., the transition to a dielectric takes place. The problem leads to parquet equations and is therefore solved only with logarithmic accuracy. A general method is developed for finding the anomalous averages corresponding to pairing, and the binding energies from asymmetric parquet vertices.     

Milliteslameters for monitoring magnetic fields in medicine and ecology

We consider the technical requirements for instruments measuring the magnetic induction of d.c., a.c., and pulsed magnetic fields which are used for medical treatment or to which humans are exposed during industrial activity. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 64–65, July, 1995.     

The generality of equations for mixed-convective heat transfer to liquids at supercritical pressure in vertical pipes

Using experimental data for helium at supercritical pressure which were obtained for ascending and descending flow in a vertical pipe, we verified the validity of a number of known equations for mixed-convective heat transfer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 6, pp. 946–951, June, 1986.     

Instrumentation and methods for low temperature measurements in high magnetic fields

There are several difficulties associated with the accurate measurement of low temperature in the presence of an intense magnetic field B. Most of the problems stem from the direct effect of the field on the thermometric properties of almost all of the comcommonly used sensors. Because the magnitude of the field effect, eg magnetoresistance, varies widely as a function of B, T, and the thermometer itself, a careful selection process is necessary to minimize the error. As an aid to such a process, a detailed comparison is presented of the field-dependent errors, Δ/T, as a function of T, of carbon, carbon-glass, germanium, and platinum resistance thermometers, thermistors, Si and GaAs diodes, thermocouples, capacitance thermometers, and several other less popular devices. Specific recommendations are made on the basis of the comparison. The related problem of magnetic field measurement is also examined, with emphasis on the recent characterizations of commercially available InAs, InSb, and GaAs Hall effect probes. From the results of measurements over the 1.5–300 K range and to fields as high as 23 T, several encouraging conclusions may be drawn concerning the performance of the sensors as magnetometers in the 1% accuracy range.     

Resistance thermometry in magnetic fields 1. Thermistors and platinum thermometers at 77 K

The effects of static magnetic field up to 16 kG on seven midget disc thermistors and three miniature platinum resistance thermometers were measured at 77 K. Corrections for the magnetoresistance of the electrical leads and solder junctions were made from data taken on a copper wire coil. A virtual temperature rise of the order of millikelvins occurs for both temperature sensors; the lead wire correction is less than a few microkelvins. The thermistors have larger magnetoresistance effects than similar types recommended for use at lower temperatures. A figure of merit comparison suggests that they are slightly less desirable than platinum thermometers in magnetic fields at liquid nitrogen temperatures.     

Use of a laser as light source for an interference study of temperature and concentration fields in liquids

The advantages of using a laser as a light source in an IAB-451 shadow instrument, used as a two-beam diffraction interferometer for studying temperature and studying temperature and concentration fields in liquids, are reported.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 1.pp. 136–139, January, 1969.     

Thin-film platinum resistance thermometer for use at low temperatures and in high magnetic fields

A thin-film platinum resistance thermometer (SDT101A, Tama Electric Work Company, Japan), which is available commercially, has useful characteristics for thermometry in the range of 20 to 300 K and in high magnetic fields up to 5 T. The Z function-table of this platinum resistance thermometer (PRT) was obtained experimentally. It was confirmed that SDT101A PRT would be useful in the temperature range of 20 to 300 K within a precision of ± 0.1 K. This confirmation was achieved by using a two-point calibration method with the Zfunction. The magnetoresistance of this PRT at 30 K is ≈ 1.5% for a magnetic field of 5 T, whose value is one order of magnitude smaller than that of a standard type PRT.     

The simulation of the processes of formation and decay of neutral particles in DC discharge plasma in an argon-oxygen mixture

Results are given of calculations of concentrations of fundamental neutral particles in the positive column of a dc discharge in an argon-oxygen mixture. The calculations are based on simultaneous solution of Boltzmann equation, vibrational kinetic equations for the ground state of O₂ molecule, and chemical kinetic equations for the ground and excited states of O₂ molecules and Ar and O atoms with the experimentally determined value of reduced intensity of electric field E/N. The results are compared with measured values of radiation intensities of lines of 811.5 nm (Ar) and 845 nm (OI) and of atmospheric band O₂(b ¹Σ _g ⁺ → X ³Σ _g ^? , 0-0).     

Speed improvement of multivariate algorithms by the method of postponed basis matrix multiplication. Part III. The use of asymmetric and generalized eigenvalue equations

It is demonstrated that the method for postponed basis matrix multiplication (PBM) applied to principal component analysis can be formulated as asymmetrical and generalized eigenvalue equations.