Measure of the closeness of crystal lattices

A numerical measure of the difference between crystal lattices is determined. The fruitfulness of the definition is demonstrated for a specific example concerning the prominence of an orientational correspondence between the body-centered crystal lattice [bcc(bct)] of α-martensite and the face-centered crystal lattice (fcc) of γ-austenite in cases where the latter is perfect and where it differs from a perfect lattice near a screw dislocation. Zh. Tekh. Fiz. 69, 60–64 (May 1999)     

Generation of electromagnetic radiation in the motion of vortices in magnetically coupled superconducting films

We examine theoretically the generation of electromagnetic radiation in the relative motion of vortex lattices in magnetically coupled films in the dc transformer geometry. We establish the conditions under which the force of mutual pinning of the vortex lattices varies according to a harmonic law as a function of the relative displacement of the vortices in the films within a given range of magnetic field inductions. In this case the equation describing the viscous flow of vortex lattices in magnetically coupled films is the same as the equation of the resistively shunted Josephson junction model. We show that magnetically coupled superconductors exhibit the properties of a Josephson element without any restrictions on the geometrical size of such a system imposed by the coherence length ξ. The frequency f of the electromagnetic radiation generated by the relative motion of vortex lattices in magnetically coupled superconductors depends on the spatial period of the vortex lattices and the velocity of relative vortex motion, which means that the frequency of the radiation can be tuned by applying a magnetic field or a current. Zh. éksp. Teor. Fiz. 113, 1319–1338 (April 1998)     

Field-induced phase transitions in magnetooptical films with a small positive anisotropy constant

We study phase transitions induced by a static magnetic field in magnetically uniaxial films with a small positive anisotropy constant. The phase diagram of these objects is determined in the H _∥-H _⊥ plane, where H _∥ and H _⊥ are, respectively, the components of the magnetizing field along and perpendicular to the surface normal. The stability boundary is located for all of the main types of domain configurations observed: a simple stripe domain structure, a stripe domain structure with periodic bending by surface distortions in the profile of the domain walls, and hexagonal lattices of cylindrical magnetic bubbles. Zh. éksp. Teor. Fiz. 111, 283–297 (January 1997)     

The magnetic field and energy of an Abrikosov vortex in an anisotropic London superconductor

The behavior of a straight Abrikosov vortex in an anisotropic uniaxial London superconductor is studied. Analytical expressions are derived that approximately describe the magnetic field in three regions: the asymptotic region, where the distance r from the vortex line is greater than λΓ (λ is the London length and Γ is the anisotropy constant), the intermediate region λ<r<λΓ, and the region r<λ. It is found that in the intermediate region with high anisotropy the component of the magnetic field along the vortex line changes sign for a certain interval of angles between the vortex line and the anisotropy axis. Because of this the interaction of parallel vortices whose plane is parallel to the anisotropy axis has a minimum and a maximum. This means that numerous metastable vortex lattices can exist. Additional terms in the vortex self-energy are obtained, and although they are smaller than the leading logarithmic term, they display a different dependence on the angle between the vortex line and the anisotropy axis. Zh. éksp. Teor. Fiz. 111, 954–963 (March 1997)     

Investigation of cordierite lattice defects by thermoluminescence experiments

Summary The thermoluminescence of α- and μ-cordierite samples has been recordedvs. temperature and wavelength. Arguments ascribing the observed emission to the easy ion exchanges characterizing cordierite lattices are advanced.     

Generalized Ginzburg-Landau equation and the properties of superconductors with Ginzburg-Landau parameter κ close to 1

An expression is derived for the free energy of a superconductor near the critical temperature, taking account of the terms of next highest order in the parameter 1−T/T _c. These terms become important for Ginzburg-Landau parameter values |κ−1|≪1, and in this case, in an external magnetic field H ₀ close to H _c2, the structure of the order parameter is determined by the relative values of the three small parameters |κ−1|, 1−T/T _c, and (H _c2−H ₀)/H _c2. Three types of lattices are investigated: triangular with one and two flux quanta per cell and square with one flux quantum per cell. Zh. éksp. Teor. Fiz. 115, 726–739 (February 1999)     

Quantum Systems on Linear Groups

Discussed are quantized dynamical systems on orthogonal and affine groups. The special stress is laid on geodetic systems with affinely-invariant kinetic energy operators. The resulting formulas show that such models may be useful in nuclear and hadronic dynamics. They differ from traditional Bohr–Mottelson models where SL(n,ℝ) is used as a so-called non-invariance group. There is an interesting relationship between classical and quantized integrable lattices. PACS: 11.30.Ly, 02.20.-a, 21.60.Ev.     

Orbital magnetism of 2D chaotic lattices

We study the orbital magnetism of 2D lattices with chaotic motion of electrons within a primitive cell. Using the temperature diagrammatic technique, we evaluate the averaged value and rms fluctuation of the magnetic response in the diffusive regime within the model of noninteracting electrons. The fluctuations of the magnetic susceptibility turn out to be large and at low temperature can be of the order of χL(k _Fl)^3/2, where k _F is the Fermi wave vector, l is the mean free path, and χL is the Landau susceptibility. In a certain region of magnetic fields the paramagnetic contribution to the averaged response is field-independent and larger than the absolute value of the Landau response. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 979–983 (25 June 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Vortex states in antiferromagnetic crystals

It is shown that axially symmetric two-dimensional nonuniform states can exist in easy-axis and cubic antiferromagnets lacking inversion symmetry, in the form of two-dimensional spatially modulated structures (magnetic vortex lattices) and isolated two-dimensional structures (vortices). The structure and equilibrium dimensions of the lattices and vortices have been determined by numerical solution of differential equations. Fiz. Tverd. Tela (St. Petersburg) 40, 1486–1493 (August 1998)     

Morita Contexts and their Lattices of Relations

We study the interaction between the lattices of relations of members of a general Morita context. The pairs of reversing-order maps are defined, which determine the dualities between the lattices of ‘closed’ relations. Under rather weak conditions, these dualities can be composed obtaining the projectivities defined by simple maps. PACS: 02.10.De,02.10.Hh.     

Tunneling of a Dipolar Bose–Einstein Condensate in an Optical Lattice

We have studied the tunneling and fluctuations of a dipolar Bose–Einstein condensate in an optical lattice, it is found that there exist the tunneling and fluctuations between lattices l and l+1, l and l−1, respectively. In particular, when the optical lattice is infinitely long and the spin excitations are in the long-wavelength limit, tunneling effects disappear between lattices l and l+1, and that l and l−1, in this case the fluctuations are a constant, and the magnetic soliton appears.     

Quantum Tunneling of Spinor Bose–Einstein Condensates in an Optical Lattice

We have studied tunneling of spinor Bose–Einstein condensate in an optical lattice. It is found that, when the system being prepared in a squeezed coherent state, there exist the quantum tunneling between lattices l and l+1, l and l−1, respectively. In particular, when the optical lattice is infinitely long and the spin excitations are in the long-wavelength limit, quantum tunneling disappear between lattices l and l+1, and that l and l−1, in this case the magnetic soliton appears.     

Thermal conductivity of a new type of regular-structure nanocomposites: PbSe in opal pores

Samples of an opal-based nanocomposite with PbSe embedded chemically into opal voids have been produced. Their thermal conductivity (in the 16–100-K range), the Seebeck coefficient (16–100 K), and electrical resistivity (5–100 K) have been measured. The thermal conductivity data permit a conclusion that a new type of substance has been produced, namely, nanocomposites having a regular structure, with each nanocomponent being a microcrystal. A concept of quasi-chemical bonding forming in nanocomponent lattices is introduced. Fiz. Tverd. Tela (St. Petersburg) 39, 586–590 (March 1997)     

Hadronic decays from the lattice

I review the lattice QCD approach to determining hadronic-decay transitions. Examples considered include ρ→ππ; b ₁→πω; hybrid meson decays and scalar meson decays. I discuss what lattices can provide to help understand the composition of hadrons.     

Anisotropy of permittivity of the hexagonal multiferroic HoMnO<Subscript>3</Subscript> in the spectral range 0.6–5.0 eV

The anisotropy of the optical properties of a single crystal of the hexagonal manganite HoMnO₃ has been investigated by spectroscopic ellipsometry in the spectral range 0.6–5.0 eV. It has been demonstrated that the optical absorption edge for the polarization E ⊥ c is determined by the intense narrow transition O(2p) → Mn(3d) centered at 1.5 eV, whereas this transition for the polarization E ‖ c is strongly suppressed and shifted toward higher energies by 0.2 eV. It has been revealed that, at the temperature T = 293 K, the spectra for both polarizations E ‖ c and E ⊥ c exhibit a broad absorption band centered at ∼2.4 eV, which was earlier observed in nonlinear spectra during optical second harmonic generation.     

Electron spectrum and stability of the saturated ferromagnetic state in a Hubbard model with strong correlations

A Hubbard model with infinite Coulomb repulsion is studied in a many-electron operator representation. A picture of the density of states is constructed using expressions for the one-particle Green’s functions of first order in 1/z. Its behavior is studied near the Fermi level, especially Condon effects. The stability of saturated ferromagnetism is examined. The corresponding critical current carrier densities are found for semielliptical and rectangular seed densities of state, and for square and cubic lattices. These results are compared with earlier work. Fiz. Tverd. Tela (St. Petersburg) 41, 1057–1063 (June 1999)     

On the connectivity index for lattices of nonintegral dimensionality

We define the connectivity indexc for an infinite graph by the requirement that to disconnect a subset of at leastV points from the rest of the graph requires the deletion of a minimum ofS(V) bonds whereS(V) ∼V ^(c−1)/c for largeV. For ad-dimensional hypercubical lattice withd integral,c=d. We construct explicit examples of lattices with nonintegral connectivity indexc, 1<c<∞. It is argued that the connectivity index is an important parameter determining the critical behaviour of Hamiltonians on these lattices.     

Intermolecular interaction in plant oils from refractive and density measurements

Refractive indices n and density ρ of three plant oils (Anise, Nigelle, and Juniper berries) have been measured in the temperature range of 10–60°C. The model of the effective electric field E′ acting on a molecule in the material, E′ = E + x4πP, with the unlimited value of the coefficient of polarization input x has been applied to the analysis of the results obtained. The value x of the oils studied have been found to be in the range of 0.193–0.269, which is smaller than a similar value for water (x _water > 0.3), known as a strong polar liquid.     

Thermal expansion of crystal lattices of germanium with different isotopic compositions

The linear thermal expansion coefficient of crystal lattices of germanium with different isotopic compositions is analyzed. Fiz. Tverd. Tela (St. Petersburg) 40, 1829–1831 (October 1998)