SVIBOR - Project code: 1-03-275

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Project code: 1-03-275


PHYSICAL PROPERTIES OF LOW-DIMENSIONAL SYSTEMS


Main researcher: BARIŠIĆ, SLAVEN (2215)


Assistants
Type of research: basic
Duration from: 01/01/91.
Papers on project (total): 75
Papers on project quoted in Current Contents: 48
Institution name: Prirodoslovno-matematički fakultet, Prirodoslovni odjeli, Zagreb (119)
Department/Institute: Department of Physics
Address: Bijenička cesta 32
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)430480
Phone: 385 (1) 430-432
Fax: 385 (1)432525
Phone: 385(1) 4555-730
Summary: The project unites efforts to deepen the understanding, by theoretical considerations, of cooperative phenomena in systems of low dimensionality, occuring in nature. One-dimensional chain conductors are being studied, with special emphasis on charge and spin density waves and the spectra of various local intrinsic defects. Two very different two-dimensional systems are under study: surfaces, and copper-oxide planes found in high Tc superconductors. As to the first, dynamical tunneling effects are under special scrutiny, while in the second attention is devoted to the effects of strongly correlated electrons on lattice deformations. Results obtained so far include the self-consistent solution of the problem of electrons interacting with surface plasmons on metal-insulator interfaces; the appearance of domain structure, which appears with the collective motion of a charge density wave in one-dimensional conductors, has been investigated under inhomogeneous conditions; the coupling of an external magnetic field to the thermodynamic properties of charge and spin density waves; it has been shown that a metastable periodical domain lattice appears during the transition from the incommensurable to the commensurable phase; the phase diagram for the sine-Gordon free energy with two potentials of different periodicities has been established; the effects of local Coulomb correlations on lattice deformations have been investigated in high Tc superconductors, and it has been found that certain phonons of high symmetry are screened, while others, which are sensitive to the superconducting transition, are not; in this it was shown analytically that the slave boson method removes one physical electron state from the Hilbert space, as a consequence of strong correlations; it was shown that the dynamical transfer of spectral strength between correlated one-particle states is sufficient for quasiparticle states to appear at half-filling.

Keywords: charge and spin density waves, phase slippage, angular resonances, domain lattices, RPA in the tight binding approach, tunneling, surface excitations, van Hove singularities, electron-phonon interactions, strong Coulomb correlations, charge and spin fluctuations, slave boson method, Raman continuum.

Research goals: We plan to investigate the hyperboloidal model of the STM (Scanning Tunneling Microscope). The aim is to calculate the influence of the interaction of the electron with the surface plasmon excitations on the tunneling current of the STM, i.e. on the images obtained by the STM. We shall investigate the dynamic domains and coherent oscillations caused by the generation of phase slip centers, as well as the influence of the external magnetic field on the thermodynamic and collective properties of charge and spin density waves. The consequencies of the nonintegrability in the phase diagram for the incommensurate-commensurate transition will be analysed. We shall discuss in detail the dielectric properties of the multiband electronic systems. In the copper oxide planes of the high Tc superconductors, we plan to study the influence of the residual interactions among the holes on the appearance of magnetic order, and try and estimate the effect of boson fluctuations on the relaxation time of fermions near the Fermi surface. We shall investigate which correlations may increase the susceptibility of the system on those deformations which split the oxygen levels. (For results, see the description of the project.)

COOPERATION - PROJECTS


  1. Name of project: CI1.0568 Properties of single crystals of high Tc superconductors
    Name of institution: CNRS, Institut za fiziku, Institut Jožef Štefan, Imperial College, IRF.
    City: Orsay, Francuska

COOPERATION - INSTITUTIONS


  1. Name of institution: Institut Jožef Štefan
    Type of institution: State institute
    Type of cooperation: Occasional exchange of information
    City: 61000 - Ljubljana, Slovenija

  2. Name of institution: University of Southern California, Department of Physics and Astronomy
    Type of cooperation: Joint publishing of scientific papers
    City: Los Angeles, SAD

  3. Name of institution: Universite Paris-Sud, Laboratoire de Physique des solides
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of experts
    City: Orsay, Francuska

  4. Name of institution: Fritz-Haber-Institut der Max-Planck-Gesellschaft
    Type of institution: State institute
    Type of cooperation: Occasional exchange of experts
    City: Berlin, Njemačka

  5. Name of institution: Universidad Autonoma de Madrid, Departamento de Fisica de la Materia Condensada
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of experts
    City: Madrid, Španjolska

  6. Name of institution: Universite Paris-Sud, Laboratoire de Physique des Solides
    Type of institution: University/Faculty
    Type of cooperation: Systematic exchange of information
    City: Orsay, Francuska

  7. Name of institution: Imperial College of Science and Technology
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of information
    City: London, Velika Britanija

  8. Name of institution: Los Alamos National Laboratory
    Type of institution: University/Faculty
    Type of cooperation: Occasional exchange of experts

  9. Name of institution: Physics Department, Brookhaven National Laboratory
    Type of institution: State institute
    Type of cooperation: Occasional exchange of experts
    City: Brookhaven, SAD
Other information about the project.
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