Charge-density waves in self-assembled halogen-bridged metal chains

Self-assembled growth of an ordered layer of Pt-Br-Pt chains on a Pt(110) surface is demonstrated. Upon slight doping with excess bromine, charge-density wave (CDW) domains separated by well-localized solutions are observed in the Br/Pt layer by scanning tunneling microscopy. Depending on annealing and adatom concentration, a global, long-range-ordered CDW ground state can be established. Angle-resolved UV photoemission data reveal the corresponding Fermi surface and its removal upon the Peierls transition. The CDW phase is stable to well above room temperature.     

Charge-density waves survive the Pauli paramagnetic limit

Measurements of the resistance of single crystals of (Per)2Au(mnt)2 have been made at magnetic fields B of up to 45 T, exceeding the anticipated Pauli paramagnetic limit of Bp approximately 37 T. The continued presence of nonlinear charge-density wave electrodynamics at B> or =37 T establishes the survival of the charge-density wave state above this limit, and the probable emergence of an inhomogeneous phase analogous to that anticipated to occur in superconductors.     

Charge-density waves in Nb1 + xS2 crystals

In-situ intercalation of surplus niobium during heating of 3R-Nb_{1 + x}S₂ (x ≥ 0.09) layered crystals in ultra-high vacuum up to 1500 K triggered an unusual inter-polytypic transition from a trigonally prismatic coordinated polytype into an octahedrally coordinated one. The new polytype contains charge-density waves with a commensurate-incommensurate phase transition, temperature-dependent on the intercalated niobium concentration. Charge-density waves in the Nb_{1 + x}S₂ compound, observed for the first time here, were studied by transmission electron diffraction and scanning tunnelling microscopy.     

Charge-density waves and superlattices in the metallic layered transition metal dichalcogenides

The d1 layer metals TaS 2 , TaSe 2 , NbSe 2 , in all their various polytypic modifications, acquire, below some appropriate temperature, phase conditions that their electromagnetic properties have previously revealed as 'anomalous'. Our present electron-microscopic studies indicate that this anomalous behaviour usually included the adoption, at some stage, of a superlattice. The size of superlattice adopted often is forecast in the pattern of satellite spotting and strong diffuse scattering found above the transition. Our conclusions are that charge-density waves and their concomitant periodic structural distortions occur in all these 4d 1 /5d 1 dichalcogenides. We have related the observed periodicities of these CDW states to the theoretical form of the parent Fermi surfaces. Particularly for the 1T octahedrally coordinated polytypes the Fermi surface is very simple and markedly two-dimensional in character, with large near-parallel walls. Such a situation is known theoretically to favour the formation of charge and spin-density waves. When they first appear, the CDWs in the 1T (and 4Hb) polytypes are incommensurate with the lattice. This condition produes a fair amount of gapping in the density of states at the Fermi level. For the simplest case of 1T-TaSe 2 , the room temperature superlattice is realized when this existing CDW rotates into an orientation for which it then become commensurate. At this first-order transition the Fermi surface energy gapping increases beyond that generated by the incommensurate CDW, as is clearly evident in the electromagnetic properties. For the trigonal prismatically coordinated polytypes, CDW formation is withheld to low temperatures, probably because of the more complex band structures. This CDW state (in the cases measured) would seem at once commensurate, even though the transition is, from a wide variety of experiments, apparently second order. A wide range of doped and intercalated materials have been used to substantiate the presence of CDWs in these compounds, and to clarify the effect that their occurrence has on the physical properties. The observations further demonstrate the distinctiveness of the transition metal dichalcogenide layer compounds, and of the group VA metals in particular.     

Brillouin scattering from isotropic metals

Brillouin scattering from isotropic metals has been analysed theoretically and excellent agreement with experiment obtained.     

Electromagnetic waves in isotropic and gyrotropic media

Maxwell’s equations are considered for waves in transparent inhomogeneous anisotropic and gyrotropic media with time dispersion. A uniaxial inhomogeneous crystal is taken for an anisotropic medium and an isotropic heterogeneous medium in a constant electric field for a gyrotropic medium. The solutions for flat-layered and cylindrical media are presented in terms of Hertz potentials. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 82–86, March, 2008.     

Charge-density and order-parameter waves in liquid and solid electrolytes in the vicinity of the critical point

The interaction between a solvent which has a second order phase transition and the solute ions leads to a periodical substructure in the vicinity of the critical point. A Bragg peak for X-ray and neutron scattering is predicted.     

Finite-amplitude waves in isotropic elastic plates

The propagation of finite-amplitude waves in a homogeneous, isotropic, stress-free elastic plate is investigated theoretically. Geometric and weak material non-linearities are included, and perturbation is used to obtain solutions of the non-linear equations of motion for harmonic generation in the waveguide. Solutions for the second-harmonic, sum, and difference-frequency components are obtained via modal decomposition. Ordinary differential equations for the modal amplitudes in the expansion of the second-order solution are obtained using a reciprocity relation. There are no restrictions on the modes or frequencies of the primary waves. Two conditions for internal resonance are quantified: phase matching, and transfer of power from the primary to the secondary wave.     

Generalized thermoelastic waves in homogeneous isotropic plates

The propagation of thermoelastic waves in homogeneous isotropic plate subjected to stress-free and rigid insulated and isothermal conditions is investigated in the context of conventional coupled thermoelasticity (CT), Lord-Shulman (LS), Green-Lindsay (GL), and Green-Nagdhi (GN) theories of thermoelasticity. Secular equations for the plate in closed form and isolated mathematical conditions for symmetric and skew-symmetric wave mode propagation in completely separate terms are derived. It is shown that the motion for SH modes gets decoupled from the rest of the motion and remains unaffected due to thermo-mechanical coupling and thermal relaxation effects. The phase velocities for SH modes have also been obtained. The results for coupled and uncoupled theories of thermoelasticity have been obtained as particular cases from the derived secular equations. At short wavelength limits the secular equations for symmetric and skew-symmetric waves in a stress-free insulated and isothermal plate reduce to Rayleigh surface waves frequency equations. Finally, the numerical solution is carried out for aluminum-epoxy composite material and the dispersion curves for symmetric and skew-symmetric wave modes are presented to illustrate and compare the theoretical results.     

Harmonic waves in layered transversely isotropic composites

The dispersive property of laminated elastic composites consisting of transversely isotropic layers is studied. Harmonic waves with various propagation directions with respect to the direction of layering are considered. Exact solutions are presented and compared with the results of the new qoutient method recently developed by one of the authors.     

Solitary waves in an isotropic ferromagnetic chain

It is shown that due to high-order terms in the Holstein-Primakoff boson-like spin operator transformation we can have a solitary wave solution even in an isotropic ferromagnetic chain.     

Laser-driven surface thermocapillary waves in isotropic and anisotropic liquids

Theoretical and experimental results on thermocapillary hydrodynamic surface waves induced in liquids by travelling spatially periodical distribution of light intensity are reported. The phase of local elevation in capillary waves is close to the phase of interference pattern when frequency is far from zero and from eigen frequency of free capillary waves. This phase difference is exactly π/2 for zero frequency.     

Shock waves in laser-pulse-irradiated metals

In an earlier paper [1] the temperature as a function of time and distance from the surface of a metal after the application of a laser pulse had been calculated. The assumption was made that only heat conduction is responsible for the dissipation of energy provided that the input fluence of the laser pulse is below the threshold for ablation. In this investigation an estimate for the pressure in the shock wave as a function of time and distance is presented. The assumption mentioned above is valid up to an input fluence of about φ=10 mJ/cm². For larger fluences (but below the ablation threshold) a correction for the dissipation of acoustic energy must be applied. The effect of surface evaporation on T_max and p_max of metals with high melting point is discussed. With fast pulses and/or relatively low velocities of sound, maximum pressures p_max of the shock wave are calculated which are higher than the corresponding stationary values (see (4)). Received: 27 April 2000 / Final version: 6 June 2000 / Accepted: 8 June 2000 / Published online: 13 September 2000     

Localized bending waves in a transversely isotropic plate

The problem of bending waves localized near the free edge of a transversely isotropic plate is investigated using the Ambartsumian higher-order plate theory which takes account of the transverse shears generated by flexural deformation. Unlike the first-order Reissner-Mindlin theory, which also takes account of transverse shears, Ambartsumian's analysis does not demand that plane normal cross-sections remain plane during bending. Within this analysis the existence of localized bending waves in transversely isotropic plates is established, and solutions of the dispersion equation obtained for different values of the elastic parameters.The analysis of frequencies of localized bending waves shows that for thick plates the effect of anisotropy can be considerable. For the particular case of vibrations of a narrow plate, from the long wave approximation a new beam vibration equation of the Timoshenko type is obtained for a transversally isotropic plate.     

Spin waves in paramagnetic metals

The excitation of spin waves in paramagnetic metals by circularly-polarized electromagnetic waves is considered. An investigation is made of the effect of boundary conditions for the magnetic moment on the amplitude of the electromagnetic-spin waves in a metal. The same investigation is carried out for the surface impedance.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 7–10, January, 1974.The author acknowledges A. Ya. Blank for proposing the subject and for numerous discussions.