We study a simple effective model for description of charge orderings in narrow band materials, i... more We study a simple effective model for description of charge orderings in narrow band materials, i.e. the spinless fermion model with repulsive intersite interaction W. The analysis is concentrated on the problem of phase separations and the effects of next-nearest neighbor hopping t2 on the charge ordered states in this system. The cases of d-dimensional (d ≥ 2) hypercubic lattices are considered for arbitrary particle concentration (0 < n < 1). Within the broken symmetry Hartree-Fock approximation the phase diagrams as a function of W and n are evaluated for representative cases. The results for t2 ≠ 0 are compared with those found for the case with nearest neighbor hopping only.
We analyse the ground state phase diagrams of the charge orderings in narrow band materials using... more We analyse the ground state phase diagrams of the charge orderings in narrow band materials using two effective models: (1) the spinless fermion model (t-W) with repulsive intersite interaction (Wij > 0) and (2) the molecular crystal model with the coupling of electrons to intramolecular (crystal field) vibrations. We present results for the case of half filled bands for d = 2 square lattice. The calculations are performed within the (broken symmetry) Hartree-Fock approximation. The study takes into consideration the effects of frustrating next-nearest-neighbour hopping (t2) on the charge ordered states in these systems. We focus on the two cases: (i) homogeneous phases and phase separations involving checkerboard charge ordering with the nesting vector Q= (π, π) only and (ii) homogeneous phases and phase separations involving two types of charge ordering: (a) checkerboard charge ordering with the nesting vector Q = (π, π), and (b) collinear (CL) charge ordering with Q = (0, π) or Q = (π, 0).
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
There is ongoing, intense, research in the field of electron charge orderings (CO) and charge den... more There is ongoing, intense, research in the field of electron charge orderings (CO) and charge density waves phenomena, due to experimental discovery of such phases in numerous important compounds. The aim of this work is to extend recent advances in the field by studying two simple effective paradigmatic models used to describe CO in narrow band materials i.e. (i) a model of correlated electrons: the so-called t-W model of spinless fermions with repulsive interaction W and (ii) the molecular crystal model with the coupling of electrons to intramolecular (crystal field) vibrations in the static limit. The finite temperature phase diagrams are evaluated at arbitrary carriers concentration for several representative cases. Our calculations are performed within the (broken symmetry) HFA for d=2 square lattice and arbitrary carriers concentration. In this contribution we focus on the effects of next-nearest-neighbor hopping on the CO states in these systems and the problem of phase separations involving checkerboard CO with the nesting vector Q=(π,π). The results we show here are an extension of our previous work on the subject.
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
We analyse the ground state phase diagrams and thermodynamic properties of charge orderings in na... more We analyse the ground state phase diagrams and thermodynamic properties of charge orderings in narrow band materials using the molecular crystal model in the static limit. We present results for the hypercubic lattices in dimensions d = 2 and d = ∞. We focus our study on the problem of phase separations involving charge orderings and the effects of next-nearest-neighbor hopping (t 2) on the charge ordered states in these systems. The ground state phase diagrams are evaluated for a few representative cases. Results for the molecular crystal model are compared with those obtained previously for the spinless fermion model with repulsive intersite interaction W .
... The results are compared with those found earlier for the attractive Hubbard model. DOI: 10.1... more ... The results are compared with those found earlier for the attractive Hubbard model. DOI: 10.1103/PhysRevB.64.104511 PACS number s : 74.20. z, 71.10.Fd, 74.20.Mn, 74.25.Dw I. INTRODUCTION The purpose of the present work is the analysis of the Penson-Kolb PK model, ...
... The PensonKolb (PK) model is one of the conceptually simplest phenomenological models for st... more ... The PensonKolb (PK) model is one of the conceptually simplest phenomenological models for study-ing superconductivity in systems with short-range, almost ... mechanism (the pair hopping term J) that is distinct from the on-site interaction in the attrac-tive Hubbard (AH) model ...
Title: Superconductivity of Systems with Coexisting Itinerant Electrons and Local Pairs. Authors:... more Title: Superconductivity of Systems with Coexisting Itinerant Electrons and Local Pairs. Authors: Czart, Wojciech R.; Robaszkiewicz, Stanislaw. Affiliation: AA(Institute of Physics, Adam Mickiewicz University, ul. Umultowska 85 ...
We study a simple effective model for description of charge orderings in narrow band materials, i... more We study a simple effective model for description of charge orderings in narrow band materials, i.e. the spinless fermion model with repulsive intersite interaction W. The analysis is concentrated on the problem of phase separations and the effects of next-nearest neighbor hopping t2 on the charge ordered states in this system. The cases of d-dimensional (d ≥ 2) hypercubic lattices are considered for arbitrary particle concentration (0 < n < 1). Within the broken symmetry Hartree-Fock approximation the phase diagrams as a function of W and n are evaluated for representative cases. The results for t2 ≠ 0 are compared with those found for the case with nearest neighbor hopping only.
We analyse the ground state phase diagrams of the charge orderings in narrow band materials using... more We analyse the ground state phase diagrams of the charge orderings in narrow band materials using two effective models: (1) the spinless fermion model (t-W) with repulsive intersite interaction (Wij > 0) and (2) the molecular crystal model with the coupling of electrons to intramolecular (crystal field) vibrations. We present results for the case of half filled bands for d = 2 square lattice. The calculations are performed within the (broken symmetry) Hartree-Fock approximation. The study takes into consideration the effects of frustrating next-nearest-neighbour hopping (t2) on the charge ordered states in these systems. We focus on the two cases: (i) homogeneous phases and phase separations involving checkerboard charge ordering with the nesting vector Q= (π, π) only and (ii) homogeneous phases and phase separations involving two types of charge ordering: (a) checkerboard charge ordering with the nesting vector Q = (π, π), and (b) collinear (CL) charge ordering with Q = (0, π) or Q = (π, 0).
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
There is ongoing, intense, research in the field of electron charge orderings (CO) and charge den... more There is ongoing, intense, research in the field of electron charge orderings (CO) and charge density waves phenomena, due to experimental discovery of such phases in numerous important compounds. The aim of this work is to extend recent advances in the field by studying two simple effective paradigmatic models used to describe CO in narrow band materials i.e. (i) a model of correlated electrons: the so-called t-W model of spinless fermions with repulsive interaction W and (ii) the molecular crystal model with the coupling of electrons to intramolecular (crystal field) vibrations in the static limit. The finite temperature phase diagrams are evaluated at arbitrary carriers concentration for several representative cases. Our calculations are performed within the (broken symmetry) HFA for d=2 square lattice and arbitrary carriers concentration. In this contribution we focus on the effects of next-nearest-neighbor hopping on the CO states in these systems and the problem of phase separations involving checkerboard CO with the nesting vector Q=(π,π). The results we show here are an extension of our previous work on the subject.
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
We analyse the ground state phase diagrams and thermodynamic properties of charge orderings in na... more We analyse the ground state phase diagrams and thermodynamic properties of charge orderings in narrow band materials using the molecular crystal model in the static limit. We present results for the hypercubic lattices in dimensions d = 2 and d = ∞. We focus our study on the problem of phase separations involving charge orderings and the effects of next-nearest-neighbor hopping (t 2) on the charge ordered states in these systems. The ground state phase diagrams are evaluated for a few representative cases. Results for the molecular crystal model are compared with those obtained previously for the spinless fermion model with repulsive intersite interaction W .
... The results are compared with those found earlier for the attractive Hubbard model. DOI: 10.1... more ... The results are compared with those found earlier for the attractive Hubbard model. DOI: 10.1103/PhysRevB.64.104511 PACS number s : 74.20. z, 71.10.Fd, 74.20.Mn, 74.25.Dw I. INTRODUCTION The purpose of the present work is the analysis of the Penson-Kolb PK model, ...
... The PensonKolb (PK) model is one of the conceptually simplest phenomenological models for st... more ... The PensonKolb (PK) model is one of the conceptually simplest phenomenological models for study-ing superconductivity in systems with short-range, almost ... mechanism (the pair hopping term J) that is distinct from the on-site interaction in the attrac-tive Hubbard (AH) model ...
Title: Superconductivity of Systems with Coexisting Itinerant Electrons and Local Pairs. Authors:... more Title: Superconductivity of Systems with Coexisting Itinerant Electrons and Local Pairs. Authors: Czart, Wojciech R.; Robaszkiewicz, Stanislaw. Affiliation: AA(Institute of Physics, Adam Mickiewicz University, ul. Umultowska 85 ...
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Papers by Wojciech Czart
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh
PACS numbers: 71.10.Fd, 71.30.+h, 71.45.Lr, 64.75.Gh