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1
Content available remote

Stopping and Straggling of Slow Atoms in Electron Gas

100%
Moneta M.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 6
1169-1176
EN
New analytical formulas for the electronic stopping power and the energy loss straggling of low velocity heavy atoms in the degenerate electron gas are calculated within the dielectric function method. The stopping and straggling effective charges of a projectile were analyzed. They are found to differ each other and to depend on the electron gas density r_{s}, on the projectile atomic number Z_{i} and on the projectile degree of ionization ζ.
2
Publication available in full text mode
Content available

Rutherford Backscattering Angular Yields under Channeling Conditions for H^+ and H^0 Projectiles

100%
Czerbniak J., Moneta M., Pudłowski G.
Acta Physica Polonica A
|
2002
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vol. 101
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issue 6
857-863
EN
The Rutherford backscattering angular scattering yields for 100 keV H^+ and H^0 projectiles from Si crystal was measured. The analysis of results using Monte Carlo simulations leads to the conclusion that H^0 beam suffers smaller dispersion than H^+ beam, when crossing crystal surface. It means that the H^0 scattering probability is smaller at large impact parameters. For greater penetration depth the channeling process turns out to be the same.
3
Content available remote

Temperature Damping of Plasmons in Nonparabolic Band

100%
Goettig S.
Acta Physica Polonica A
|
1991
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vol. 79
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issue 2-3
333-336
EN
Damping of plasmons in the nonparabolic free-carrier band of a semiconductor is considered within RPA. Due to the nonparabolic band shape the temperature broadening of plasmons is strongly reduced and even at high temperatures plasmons with large wavevectors may exist as undamped excitations.
4
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Electron Spectrum and Dieleclric Susceptibility of the Hubbard Model with Local Lattice Anharmonicity

63%
Stasyuk I., Shvaika A.
Acta Physica Polonica A
|
1994
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vol. 85
|
issue 2
363-366
EN
The investigation of single-electron spectrum of the Hubbard model with local lattice anharmonicity is performed. The influence of the interaction with the vibrational subsystem on the effective exchange constant is considered. The static transverse dielectric susceptibility of the model is calculated. Analysis of the possible dielectric anomalies is performed on this basis.
5
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Dielectric Properties and Electron Spectrum of the Müller Model in the High-Temperature Superconductivity Theory

63%
Stasyuk I., Shvaika A.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 2
293-313
EN
The paper is devoted to the investigation of the single-electron excitation spectrum, effective exchange interaction and dielectric susceptibility of the Muller model for high-temperature superconductivity. It is shown that the interaction with the anharmonic vibration mode leads to the additional splitting of the electron bands and their narrowing. The sign of the effective exchange interaction between electrons depends on the local state of the vibration subsystem. The electron and pseudospin (lattice) contributions to the transverse dielectric susceptibility are investigated.
6
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Effect of Nonequilibrium Plasmons on Electron-Plasmon Interactions in Semiconductors

63%
Popov V. V., Bagaeva T. Y.
Acta Physica Polonica A
|
1997
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vol. 92
|
issue 5
963-966
EN
The effect of nonequilibrium plasmons on the steady-state high-dc-field response of electron gas in n-GaAs is numerically studied via iterative procedure using the Monte Carlo simulation algorithm for hot-electron transport and the Boltzmann equation for plasmons. The electron population inversion in wave vector space along the electric field is predicted to exist for fields in excess of about 10 kVcm. The plasmon distribution disturbances leave the steady-state velocity at low fields almost unaffected but lead to reduction of that up to 10% for fields around and above the maximum of the velocity-field characteristics.
7
Publication available in full text mode
Content available

Static Local Field Factor and Ground State Properties of Interacting Electron Gas

63%
Sarkar A., Haldar S., Roy D., Sen D.
Acta Physica Polonica A
|
2004
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vol. 106
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issue 4
497-514
EN
In the most general case, the calculation of the static local field factor G(q) for the unpolarised electron gas requires the knowledge of exchange-correlation energy functionals for both the parallel and antiparallel relative spin orientations of the electron gas system. Accurate density interpolation formulae using the quantum Monte Carlo data of Ceperley-Alder for the correlation energy of electron gas in both the "para" and "ferro" states, respectively, in the given density range are used for the calculation of G( q). Fulfilment of relevant consistency criteria is ensured and the local field factor so obtained renders significant improvement of ab initio pseudopotential calculation of effective interaction of Al. The Levin like interpolant of the correlation energy Ceperley-Alder data has been further used to study the ground state properties of the electron gas. It is also noted that a better understanding of the interacting electron gas properties requires a more accurate spin interpolation formula for the correlation energy than the existing ones.
8
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Optical Absorption in Periodic InN:In Structures

63%
Plotnikov D., Shubina T., Jmerik V., Semenov A., Ivanov S.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
191-196
EN
Optical absorption measurements were exploited to study periodic InN:In structures grown by plasma-assisted molecular beam epitaxy with the thickness of the metallic inclusions varied from 2 to 48 monolayers. We demonstrate that the observed higher-energy shift of an effective absorption edge may be due to In depletion of the InN matrix via the coalescence of In into large clusters, accompanied by the respective higher-energy shift of the Mie resonance. The relevant uncertainty in the optical gap of InN is discussed.
9
Content available remote

Stopping of Slow H-, He-, Li- and Be-Like Projectiles in Electron Gas

63%
Moneta M.
Acta Physica Polonica A
|
1998
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vol. 93
|
issue 5-6
775-783
EN
Results of calculations of the electronic stopping power and the energy loss straggling for low velocity H-, He-, Li- and Be-like projectiles in the degenerate electron gas are reported. The Hartree-Fock-Slater description of the projectile and the dielectric function method were used. The size parameter Z__{min} of the charge distributions calculated from a variational principle depends on the characteristics of the medium. The stopping and straggling effective charges Z_{ef} of a projectile were analysed. They were found to differ with each other and to depend on the one-electron radius r_{s}, on the projectile atomic number Z_{i} and on the number of electrons N_{i} carried by the projectile.
10
Content available remote

Correlation-Driven Metal-Insulator Transitions

63%
Honig J.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 1
141-156
EN
The effect of correlation-driven electronic transitions are described for the V_{2}O_{3}, NiS_{2-x}Se_{x}, and Fe_{3}O_{4} systems. The various tranformations can all be rationalized in terms of elementary concepts pertaining to the Mott-Hubbard intraatomic electronic interactions or in terms of an order-disorder formalism involving Coulomb interactions among electrons on adjacent sites. Attention is directed to some outstanding issues that require further resolution.
11
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Investigation of Phonons in HgCdMnTe Using Far-Infrared Reflectivity

63%
Dudziak E., Bożym J., Pruchnik D., Baran J.
Acta Physica Polonica A
|
1993
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vol. 84
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issue 3
595-598
EN
The first reflectivity spectra of Hg_{1-x-y}Cd_{x}Mn_{y}Te with 0.03 < x < 0.1 and 0 < y < 0.05 were measured in the spectral region 700-30 cm^{-1} at 300 K and 90 K. The quaternary alloys measured show three mode behaviour. The experimental results are interpreted by using a classical dynamic dielectric function model.
12
Publication available in full text mode
Content available

Characteristics of H- to Be-like Ions Immersed in Electron Gas

63%
Moneta M.
Acta Physica Polonica A
|
2001
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vol. 99
|
issue 6
643-653
EN
The electronic characteristics of H- to Be-like ions immersed in degenerate electron gas were calculated. The ion was described within the Hartree- Fock-Slater formalism and the medium by the dielectric function. The ion's electrons repulsion, screening and exchange effects and, additionally, the self-binding of an electron due to the polarisation of the medium were included in the description. The results were compared with the reference corresponding to the characteristics for ions in vacuum.
13
Content available remote

Many-Body Effects and Bandgap Renormalization in H-Shaped Quantum Wires

63%
Nozari K., Akbari S., Fayeghi F., Mirzaie M.
Acta Physica Polonica A
|
2009
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vol. 115
|
issue 3
721-731
EN
In this paper, bound states energies and corresponding wave functions of H-shaped quantum wires are calculated numerically in the presence of the external magnetic and electric fields. This analysis was done within the Landau gauge. With a suitable definition of the external confinement potential, we present a numerical algorithm to calculate the profile of the probability distribution of charge carriers. Our analysis shows that in the presence of the external electric and magnetic fields, bound state properties of the carriers are sensitive functions of an asymmetric parameter a= W_{x}/W_{y} which measures the relative width of the quantum well in two directions. We also study many-body effect of the bandgap renormalization in this quasi-one-dimensional system within the dynamical random phase approximation in its leading order.
14
Content available remote

Electronic Correlations and Electron-Molecular Vibration Coupling in Pentamerized Charge Transfer Crystals

63%
Yartsev V., Garrigou-Lagrange C.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 4-5
819-822
EN
A cluster approach is used for a theoretical description of the optical properties of pentamerized low-dimensional molecular crystals. Electronic correlations are taken into account explicitly in the Hubbard model for 1, 2, 3, 4 and 5 electrons in a linear pentamer, as well as coupling of electrons to the totally symmetric intramolecular vibrations. Calculated absorbance is compared to the measured one in pentamerized salt of TCNQ and TTF molecules.
15
Content available remote

Electron Liquids in Coupled Quantum Wells

51%
Świerkowski L., Szymański J., Neilson D.
Acta Physica Polonica A
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1993
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vol. 84
|
issue 3
445-457
EN
A system comprising of two adjacent layers of conduction electrons or alternatively a layer of electrons and a layer of holes can exhibit novel instabilities in the liquid phase towards inhomogeneous ground states. The carriers in the two layers can couple to each other through the Coulomb interaction but they are not permitted to tunnel so that the charges in one layer act as a polarisable background for the other layer. The presence of a second layer encourages the formation of novel ground states with inhomogeneous density distributions. We find theoretical evidence for the existence of charge density wave ground states and also a coupled Wigner crystal. These exist at much higher densities than the Wigner crystallisation density for the single layer case. The existence of these inhomogeneous ground states leads to significant modifications of the low lying excitation spectrum in the uniform liquid phase. Near the transitions to both the charge density wave and the coupled Wigner crystal phases we find evidence of the development in the liquid phase of new soft mode excitations of finite wave number q that are precursors of the inhomogeneous ground states. Near the transition to the coupled Wigner crystal we observe a strong tendency of the single particle excitation spectrum for the liquid phase to renormalise into a single line that has a dispersion closely resembling the phonon dispersion curve for the solid.
16
Content available remote

The Primary Role of Ionic Polarizability in Exotic Superconductivity

51%
Weger M.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 4-5
723-733
EN
The ionic polarizability of organic metals and of high-T_{c} cuprates is very high while the density of conduction electrons is low. As a result, the ionic polarizability screens out the electronic polarizability for states very close to the Fermi surface. The cut-off is determined by the dispersion of the ionic polarizability. The electron-phonon matrix element is very large for the ionically screened states, and is the cut-off for the electronically screened states. Therefore, the McMillan coupling constant λ_{ph} is very large at very low energies, and has a low energy cut-off. This model accounts for both normal and superconducting state anomalies in organic metals, as well as cuprates.
17
Content available remote

AC Electrical Conductivity and Dielectric Properties of Perovskite (Pb,Ca)TiO_3 Ceramic

51%
El-Mallah H.
Acta Physica Polonica A
|
2012
|
vol. 122
|
issue 1
174-179
EN
Pb_{1 - x }Ca_{x}TiO_3 perovskite crystalline structure with x = 0, 0.2, 0.6, 0.7, and 0.8 were prepared by mixture method. The ac conductivity and dielectric properties of the studied bulk compositions have been investigated in the frequency range 1 × 10^3 - 5 × 10^6 Hz and temperature range 303-473 K. The experimental results indicate that the ac conductivity σ_{ac}(ω), dielectric constant ε' and dielectric loss ε" depend on the temperature and frequency. The ac conductivity was found to obey the power law ω^{S} with the frequency exponent S > 1 decreasing with increasing temperature. The present results are compared to the principal theories that describe the universal dielectric response behavior. Values of dielectric constant ε' and dielectric loss ε" were found to be temperature and frequency dependent and the maximum barrier height W_{m} is calculated.
18
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Monte Carlo Simulations of Spatial Correlations of Charged Centers in δ-Doped Layers

51%
Sobkowicz P., Wilamowski Z., Kossut J.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 4
645-648
EN
Results of Monte Carlo simulations of a 2D system of charged donors are presented. They enable to study the effects related to a spatial correlation of donor charges located on a random donor matrix. A qualitative difference between DX^{+} and DX¯ models is observed. In the first case, strong temperature dependence of the correlations and a "freezing-like" behaviour is found. The origin of the freezing is traced to the random distribution of donor sites by comparing the system with a liquid-like model where the charges may assume arbitrary positions within a plane. In the second case only nearest-neighbour correlations are observed. The simulations have direct application in analysis of the behaviour of the DX centers in the GaAs planarly doped with Si.
19
Content available remote

Optical Properties of LiNbO₃-Ag Nanocomposites

51%
Bolesta I., Vakiv M., Haiduchok V., Kushnir O., Demchuk A., Nastyshyn S., Gamernyk R.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 4
860-863
EN
The article presents the experimental results of the investigation of the absorption spectra and nonlinear refraction of the metal-dielectric nanocomposite that contains the lithium niobate pyroelectric crystal coated with the silver nanofilms on its surface. The atomic force microscopy surface research of these crystals with and without films are also provided. The nanowidth silver films impact on optical spectra and nonlinear refraction of LiNbO₃-Ag nanocomposite was analyzed depending on the sign of the side charge of the crystal, that contain nanofilms.
20
Content available remote

Plasma Edge Modification in Strongly Compensated Semiconductors

51%
Szuszkiewicz W., Dybko K., Bardyszewski W., Julien C.
Acta Physica Polonica A
|
1995
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vol. 88
|
issue 5
1048-1052
EN
We demonstrate that the electron-impurity interaction can modify the reflectivity in the vicinity of plasma minimum giving rise to a small dip on the plasma edge. Experimental spectra taken for Hg_{1-x}Co_{x}Se for x < 0.02 at various temperatures confirm this theoretical prediction. The position of the structure can be used to determine the plasma frequency in highly compensated materials at low temperatures.
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