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.     

ESR and ENDOR studies of solitons and polarons in conjugated polymers

Nonlinear excitations such as solitons and polarons in conjugated polymers carry spins. In this case electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) provide unique methods to determine their wave functions. In this review article, the case of solitons in polyacetylene, CH_x, and polarons in an electroluminescent polymer, poly(paraphenylene vinylene) (PPV) are discussed as typical examples. High-resolution proton ENDOR spectra, obtained with stretch-oriented samples, yield the half extension of the excitations of 18 carbon atoms and 4 phenyl rings for CH_x and PPV, respectively. These extensions are well described by the theories in the case of finite electron correlation. In addition, light-induced ESR technique is shown to be useful in obtaining site-selective information of spin distribution in the case of PPV derivatives, as well as the excitation spectra of polarons.     

Correlation functions of the 1-D coulomb gas,solitons and the 1-D Fermi gas

We study various correlation functions of the classical one-dimensional two component Coulomb gas (1-D CG). As a first example the dielectric function _q is considered. Explicit expressions for the first two terms of the long-wavelength expansion of _q ^-1 are rigorously derived by extending the method of Edwards and Lenard. On account of the equivalence between the 1-D CG and the sine-Gordon (SG) model _q can also be viewed as a correlation function of the SG field and the effects of small amplitude oscillations and of solitons can be traced in _q . We show that the nonmetallic nature of the 1-D CG is solely attributable to solitons. A similar analysis is carried out for other correlation functions. We establish a relation between these correlation functions and certain response functions of a one-dimensional Fermi gas by exploiting the known equivalence between the backward-scattering model of the Fermi gas and a 2-D CG on the surface of a cylinder and by investigating the conditions under which this 2-D CG can be considered one-dimensional.     

Degeneracy of solitons and polarons in polyacetylene for translation between nearest neighbour sites

In polyacetylene, there are solitons with two different interface natures, one connecting oppositely dimerized chains by two single bonds and another by two double bonds. There are also polarons of two kinds, one with the center on a double bond and another on a single bond. These two kinds of solitons and polarons are converted to each other by translation between nearest neighbour sites. They have apparently different electronic structures but are degenerate in energy and have the same lattice structure. The origin of the degeneracy is disclosed.     

Dynamics of charge solitons in 1-D arrays of Josephson junctions

A 1-D array of Josephson coupled superconducting grains whose kinetic inductance dominates over the Josephson inductance is studied. We show that in this limit excess Cooper pairs in the array give rise to charge solitons via polarization of the grains. We analyze the dynamics of these macroscopic topological excitations, and find that their classical relativistic motion leads to saturation branches in the I-V characteristic of the array. When the dephasing length of the charge soliton is larger than the length of the array, we expect that it behaves quantum mechanically. We study the dynamics of quantum charge solitons in a ring-shaped array biased by an external flux, and show that they can exhibit phenomena like persistent current and coherent current oscillations.     

PT L3 near edge structure of halogen-bridged mixed-valence pt complexes and pd-pt mixed-metal complexes

X-ray absorption near edge structure (XANES) of halogen-bridged mixed-valence Pt complexes and halogen-bridged Pd-Pt mixed-metal complexes have been measured using synchrotron radiation with a high energy resolution. In Pd-Pt mixed metal complexes, we demonstrate that the degree of the valence is estimated from the intensity of the white line at the Pt L₃ edge. In the mixed-valence complexes, the electron system is proved to be the Peierls insulator with a charge density wave of renormalized d electrons of Pt, where the total valence of Pt^IV- and Pt¹¹ is conserved without excess electrons from ligands or anions.     

Flame synthesis of 1-D complex metal oxide nanomaterials

One dimensional (1-D) complex metal oxide nanomaterials, such as ternary oxides, doped oxides, and hierarchical structures containing several oxides, not only benefit from large aspect ratios, but also offer exciting opportunities to design materials with desired properties by tuning their chemical compositions and tailoring their sizes and morphologies at the nanometer scale. Flame synthesis is an attractive method to grow 1-D complex metal oxide nanostructures because of its high temperature, scalability, low-cost and rapid growth rate. Here, we present three new combined flame synthesis methods: (1) simultaneous vapor–vapor growth, (2) simultaneous solid–vapor growth, and (3) sequential solid–vapor growth, to grow 1-D complex metal oxide nanostructures with well-defined compositions and morphologies. These three methods combine the previously reported flame vapor deposition and solid diffusion growth methods that were separately used to grow 1-D simple binary metal oxide nanostructures, and significantly advance the capabilities of existing flame synthesis methods for the growth of 1-D nanomaterials. The first method, simultaneous vapor–vapor growth, combines the flame vapor deposition growth of two different metal oxides by oxidizing and evaporating two different metal sources. With this we have successfully grown W-doped MoO₃ nanoplates and nanoflowers. In the second method, simultaneous solid–vapor growth, one precursor is again provided by oxidizing and evaporating metal oxide from a metal, while the other precursor diffuses out from a different growth substrate. With this we have successfully grown ternary Cu₃Mo₂O₉ nanowires. The third method, sequential solid–vapor growth, essentially uses the 1-D nanostructures firstly grown by solid diffusion as the substrates for subsequent flame vapor deposition. With this we have successfully grown hierarchical CuO/MoO₃ core/shell nanowires and MoO₃-branched CuO nanowires. We believe that these three new combined flame synthesis methods will provide a general platform for the synthesis of 1-D complex metal oxide nanostructures with tailored properties.     

Motion of complexes of 3D-laser solitons

We reveal the existence of a wide class of stable solid-like 3D-dissipative soliton complexes with weak in-phase and antiphase coupling. Their 3D-orientation and motion depend on the ratio of coefficients of spatial and spectral filtering and on the symmetry of distributions of intensity and energy flows in complexes. Presented are motionless, moving in line, rotating, and moving along nonplanar trajectory complexes, as well as a number of scenarios of collisions of moving complexes.     

Studies on 1-D metallic complexes at microwave frequencies

The conductivity and dielectric constant at 35 GHz are reported for eight partially oxidised tetracyanoplatinate and bis (oxalato) platinate salts. Whenever possible the results are compared with those obtained from dc measurements.     

Near-infrared spatial solitons in heavy metal oxide glasses

We demonstrate two-dimensional spatial solitons excited by near-infrared picosecond pulses in Kerr-like heavy metal oxide glasses with a nonlinearity one order of magnitude larger than in fused silica. Solitons were obtained at 820 nm owing to the presence of multiphoton absorption, which prevented catastrophic collapse.     

Collisions of complexes of weakly coupled laser solitons

Different scenarios of collisions of complexes of weakly coupled solitons moving in antiparallel directions in a wide-aperture class-A laser with saturable absorption are found by numerical simulation. Depending on the impact parameter and the phase difference of the initial complexes, they can adhere to each other or form new complexes composed of both initial complexes, while the number of solitons can change from their total disappearance to the extension of the region of generation over the whole transverse cross section of the laser.     

Drift ion acoustic solitons in an inhomogeneous 2-D quantum magnetoplasma

Linear and nonlinear propagation characteristics of quantum drift ion acoustic waves are investigated in an inhomogeneous two-dimensional plasma employing the quantum hydrodynamic (QHD) model. In this regard, the dispersion relation of the drift ion acoustic waves is derived and limiting cases are discussed. In order to study the drift ion acoustic solitons, nonlinear quantum Kadomstev-Petviashvilli (KP) equation in an inhomogeneous quantum plasma is derived using the drift approximation. The solution of quantum KP equation using the tangent hyperbolic (tanh) method is also presented. The variation of the soliton with the quantum Bohm potential, the ratio of drift to soliton velocity in the co-moving frame, , and the increasing magnetic field are also investigated. It is found that the increasing number density decreases the amplitude of the soliton. It is also shown that the fast drift soliton (i.e., v_*>u) decreases whereas the slow drift soliton (i.e., v_*<u) increases the amplitude of the soliton. Finally, it is shown that the increasing magnetic field increases the amplitude of the quantum drift ion acoustic soliton. The stability of the quantum KP equation is also investigated. The relevance of the present investigation in dense astrophysical environments is also pointed out.