Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 6

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Thermodynamics of the Generalized Spin-One-Half Falicov-Kimball Model in Two Dimensions

100%
Žonda M., Farkašovský P., Čenčariková H.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
104-106
EN
The extrapolation of small-cluster exact-diagonalization calculations and the Monte Carlo method is used to study the spin-one-half Falicov-Kimball model extended by the spin-dependent Coulomb interaction (J) between the localized f and itinerant d electrons as well as the on-site Coulomb interaction (U_{ff}) between the localized f electrons. It is shown that in the symmetric case the ground-state phase diagram of the model has an extremely simple structure that consists of only two phases, and namely, the charge-density-wave phase and the spin-density-wave phase. The nonzero temperature studies showed that these phases persist also at finite temperatures. The same calculations that we performed for unsymmetric case showed that charge and spin ordering can be destroyed simultaneously or consecutively.
2
Content available remote

Ground States of the Spin-One-Half Falicov-Kimball Model with Hund's Rule Coupling in Two Dimensions

100%
Čenčariková H., Farkašovský P., Tomašovičová N., Žonda M.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
101-103
EN
The spin-one-half Falicov-Kimball model with spin-dependent on-site interaction between localized (f) and itinerant (d) electrons is studied by small-cluster exact-diagonalization calculations and a well-controlled approximative method in two dimensions. The results obtained are used to categorize the ground-state configurations according to common features (charge and spin ordering) for all f and d electron concentrations (n_f and n_d) on finite square lattices. It is shown that only a few configuration types form the basic structure of the charge phase diagram in the n_f-n_d plane. In particular, the largest regions of stability correspond to the phase segregated configurations and configurations that can be considered as mixtures of chessboard configurations and the full (empty) lattice. Since the magnetic phase diagram is much richer than the charge phase diagram, the magnetic superstructures are examined only at selected values of f and d electron concentrations.
3
Content available remote

Diagrammatic Perturbation Technique for a Quantum Dot Connected to Superconducting Leads

100%
Pokorný V., Janiš V., Novotný T., Žonda M.
|
|
vol. 126
|
issue 1
352-353
EN
We study spectral properties of a quantum dot attached to two superconductors with nonzero phase difference. The system is described as a single-impurity Anderson model coupled to BCS superconducting leads. We utilize diagrammatic perturbation expansion in the Coulomb interaction to capture relevant physical phenomena, particularly the effect of the Coulomb interaction on the Andreev bound states present in the electronic spectrum. Results of the Hartree-Fock and the random phase approximations at zero temperature are presented.
4
Content available remote

Simplified Parquet Equations for the Anderson Impurity Model: Comparison with Numerically Exact Solutions

100%
Pokorný V., Žonda M., Kauch A., Janiš V.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1042-1044
EN
We use an analytic solver for the single-impurity Anderson model based on simplified parquet equations to describe the Kondo asymptotics. This scheme uses a two-particle self-consistency to control the strong-coupling Kondo critical behavior of this model at half filling. The equations can be written in the real-frequency representation, which gives us direct access to spectral functions unlike numerical schemes in the Matsubara formalism. We compare our results to those obtained by second-order perturbation theory, numerical renormalization group, and continuous-time quantum Monte Carlo in order to assess the reliability of this approximation.
5
Content available remote

Ground States of the Falicov-Kimball Model Extended by Nonlocal Coulomb Interactions

100%
Čenčariková H., Farkašovský P., Žonda M.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
287-290
EN
The small-cluster exact-diagonalizations are used to study the ground states of the Falicov-Kimball model extended by nonlocal Coulomb interactions (the nearest-neighbour interaction U_{nn} and the correlated hopping t'). It is shown that the ground-state phase diagrams found for the conventional Falicov-Kimball model are strongly changed when the nonlocal interactions are added. This is illustrated for two selected values of the on-site Coulomb interaction (U) that represent typical behaviours of the model in the intermediate and strong coupling limit. A number of remarkable results are found. (i) The phase separation takes place for a wide range of U_{nn} and t' in both interaction limits. (ii) New types of inhomogeneous charge ordering are observed for nonzero U_{nn} and t'. (iii) Depending on the values of U_{nn} and t', the model is able to describe both the continuous as well as discontinuous changes of the f-electron occupation number.
6
Content available remote

The Influence of Lattice Defects on the Ground-State Properties of the Falicov-Kimball Model in Two Dimensions

100%
Žonda M., Farkašovský P., Čenčariková H.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
291-294
EN
The influence of lattice defects (vacancies) on the ground-state properties of the spinless Falicov-Kimball model is studied by a well-controlled numerical method in two dimensions. It is shown that in the presence of vacancies (distributed randomly) the ground states of the Falicov-Kimball model are phase separated for small f-electron concentrations n_f and exhibit the long-range order for n_f near the half-filled band case n_f=1/2. In addition, the dependence of average f-orbital occupancy on the concentration of vacancies is calculated for a wide range of model parameters. The resultant behaviours are used to interpret the experimental data obtained for the mixed-valence system Sm_{1-x}B_6.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.