Projects / Programmes
Theory of Condensed Matter and Statistical Physics
January 1, 1999
- December 31, 2003
| Code |
Science |
Field |
Subfield |
| 1.02.00 |
Natural sciences and mathematics |
Physics |
|
| Code |
Science |
Field |
| P190 |
Natural sciences and mathematics |
Mathematical and general theoretical physics, classical mechanics, quantum mechanics, relativity, gravitation, statistical physics, thermodynamics |
| P250 |
Natural sciences and mathematics |
Condensed matter: structure, thermal and mechanical properties, crystallography, phase equilibria |
| P260 |
Natural sciences and mathematics |
Condensed matter: electronic structure, electrical, magnetic and optical properties, supraconductors, magnetic resonance, relaxation, spectroscopy |
Researchers (11)
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0106 |
Jožef Stefan Institute |
Ljubljana |
5051606000 |
90,753 |
Abstract
In the theory of strongly correlated electrons and high temperatur superconductivity we have continued our research of the Hall response. We have shown that the ground state Hall constant in the slow motion limit can be expressed directly in terms of the Drude weight for the conductivity. We have also treated the plasmon excited states in copper high temperature superconductors (cuprates) and demonstrated that these states are anomalously damped.
The one particle distribution function for the planar system of strongly correlated electrons (t-J model) has been investigated in the limit of weak doping. The distribution function shows an anomalous wave vector dependence, which can be interpreted in accordance with the Luttinger principle as a trace of the emerging Fermi surface.
In the spectral functions for planar cuprates we found at various hole concentrations a pseudo-gap and determined the transverse optical conductivity.
We have explored the properties of the bipolaron in a 1D Holstein-Hubbard model with dynamical quantum phonons. The two-site bipolaron has a significantly reduced mass and isotope effect compared to the on-site bipolaron, and is bound in the strong coupling regime up to twice the Hubbard parameter U.
Using a recently developed Lanczos technique we have studied numerically finite-temperature properties of the 2D Kondo lattice model at various fillings of the conduction band. At half filling the quasiparticle gap governs physical properties of the chemical potential and the charge susceptibility at small temperatures. A spin gap in the intermediate coupling regime leads to exponential drop of the spin susceptibility at low temperatures. Unusual scaling of spin susceptibility is found in the intermediate temperature range.
We have introduced a new spherical random-bond---random-field (SRBRF) model of relaxor ferroelectrics such as lead magnesium niobate (PMN) and lantanum lead zirconium titanate (PLZT). It has been assumed that polar clusters, which exist in these substances, can be treated in a manner analogous to the dipolar degrees of freedom in dipolar glasses, however, their magnitude varies continuously subject only to the global spherical condition. In collaboration with two experimental groups at J. Stefan Institute we have applied the SRBRF model to explain the lineshape of NMR spectra in PMN and the nonlinear dielectric constant in PMN and PLZT.
We have used numerical simulations to study various models of self-organized criticality. In the model of granular flow we have shown that temporally disordered local relaxation rules lead to a global state of the system, which is characterized by a multifractal spectral function. The dynamic phase transition at a critical value of the control parameter in the stochastic cellular automaton has been investigated. We have shown that due to the dynamic conservation of the number of particles, the transition exhibits certain properties of three-dimensional directed percolation. By means of numerical simulations we have studied the Barkhausen noise in a model with extended domain walls and nonmagnetic impurities. Within the same model we have investigated the correlations of triggering noise fields, which are induced by the self-consistent evolution of the system in the limit of infinitely slow driving.
The stability and morfology of reconstructed (100) surfaces of noble metals were investigated. Together with a group from Innsbruck we have developed a model of elastic interactions between the steps on the (100) surface of platinum. We have also studied surface vibrations and their effect on the surface stability, and found that they enhance the stability of some reconstructed surfaces.
Most important scientific results
Final report
Most important socioeconomically and culturally relevant results
Final report
