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Tytuł:
Point-Contact I-V Characteristics of the Electroluminescent ZnS:Mn,Cu Thin Films Studied by STM
Autorzy:
Szuba, S.
Czajka, R.
Gordon, W. S.
Polewska, W.
Raułuszkiewicz, J.
Reich, A.
Powiązania:
https://bibliotekanauki.pl/articles/1879824.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
73.40.Gk
73.60.Fw
Opis:
STM images of ZnS:Mn,Cu thin films and spatially resolved current-voltage characteristics are shown. The results make possible to estimate the morphology and conductivity distribution with nanometer resolution.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 171-174
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic Affinity of Elastomer-Solvent System and Barrier Properties of Elastomer Materials
Autorzy:
Krzemińska, S.
Rzymski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1400497.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.60.Lf
61.25.hp
64.75.Bc
81.05.Lg
Opis:
The aim of the study was to determine whether it is possible to correlate directly the barrier properties of elastomer materials assessed on the basis of the breakthrough time $t_{p}$ with the thermodynamic affinity of the elastomer-solvent system, characterized by their solubility parameters δ. According to EN ISO 6529:2001 standard, breakthrough time is defined as the time elapsing from the moment that the tested material sample gets in contact with the chemical to the moment in that a specified amount of the substance appears on the other side of the sample. Cured butyl rubber (IIR) in the form of flat membranes were tested in the study. For the nonpolar rubber-polar or rubber-nonpolar solvent systems it has been found that significant differences in rubber and solvent solubility parameters not in every case leads to better resistance to permeation. The properties of the permeating chemical and the rubber, including its polarity, shape, and molecule dimension of the solvent, are of considerable importance. A marked disparity of breakthrough times were observed for the permeation of polar or nonpolar solvents despite similar values of their solvent solubility parameter. The breakthrough time of the solvent from the homologous series (pentane, hexane and heptane) is determined not only by the rubber and solvent solubility parameters but by the size of the chemical molecule as well. Therefore, for the assessment of material barrier properties the thermodynamic affinity or dissimilarity of the elastomer and the permeating solvent is only semiquantitative in character.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 146-150
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure-Driven Reordering of Valence Band States in AlGaN/AlN Quantum Wells
Autorzy:
Łepkowski, S.
Bardyszewski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1403639.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
78.67.De
62.50.-p
Opis:
We study theoretically the influence of external hydrostatic pressure on the valence band structure in [0001]-oriented $Al_{x}Ga_{1-x}N$/AlN quantum wells used in deep-ultraviolet light emitting devices. The calculations performed using the multi-band k·p method with excitonic effects show that for $Al_{x}Ga_{1-x}N$/AlN quantum wells with x = 0.7 and quantum well width of 1.5 nm, reordering of the topmost valence subbands having different symmetries occurs with increasing pressure. In these structures, at low pressure values the topmost valence level is of $\Gamma p_9$ symmetry whereas it changes to the $\Gamma p_7$ state for pressures about 2.5 GPa. We also find that the excitonic effects increase the critical value of pressure at which the change in the polarization of the emitted light occurs to 7 GPa. This behavior is opposite to the pressure-dependent reordering of the topmost valence band states in thin GaN/AlGaN quantum wells which occurs from $\Gamma p_7$ to $\Gamma p_9$ states.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 1029-1030
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Diagrams of the Penson-Kolb-Hubbard Model with Repulsive Pair-Hopping Interaction
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1398641.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We study the extended Hubbard model with on-site density-density U and intersite pair hopping J interactions, i.e. the Penson-Kolb-Hubbard model. This report focuses mainly on the properties of the model at T ≥q 0 in the case of repulsive J (J < 0) which may stabilize superconductivity with η-pairing. The analysis is performed within the (broken symmetry) Hartree-Fock approximation for arbitrary interaction parameters (J < 0 and U) and electron concentration (0 < n < 2) on the d = 2 square lattice. The phase diagrams of the model at T=0 and at finite temperatures are examined taking into account magnetic and charge-ordered phases and superconducting states with η- and s-wave pairing.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 613-616
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Symmetry of the Top Valence Band States in GaN/AlGaN Quantum Wells and its Influence on the Polarization of Emitted Light
Autorzy:
Bardyszewski, W.
Łepkowski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1492909.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.40.Fy
78.20.Bh
78.30.Fs
Opis:
We show theoretically that for narrow GaN/AlGaN quantum wells, lattice matched to GaN substrate/buffer and grown along the (0001) crystallographic direction the topmost valence subband symmetry depends critically on such parameters as quantum well thickness and barrier composition. This effect determines polarization of the emitted light. It is noted that the symmetry of the topmost valence band level is sensitive to the values of the $D_3$ and $D_4$ deformation potentials and can be employed in verification of existing literature values of these parameters.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 894-896
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Problems in Quantitative Auger Analysis of Metallic Alloys
Autorzy:
Mróz, S.
Doliński, W.
Powiązania:
https://bibliotekanauki.pl/articles/1892438.pdf
Data publikacji:
1992-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.20.Fv
68.35.Dv
Opis:
Factors determining the Auger signal intensity are discussed. It is indicated that using standards is the only reasonable way for quantitative Auger analysis (QAA). Approaches to QAA without and with matrix corrections are presented. It is shown that the matrix correction connected with atomic concentrations of pure standards is the most important and that the other matrix corrections (e.g. those connected with the attenuation length and backscattering factor) do not improve appreciably the QAA exactness in many examples taken from the literature. The examples indicate that in the case of metallic alloys the properly performed QAA gives the relative atomic concentrations with the error not exceeding few percent.
Źródło:
Acta Physica Polonica A; 1992, 81, 2; 201-210
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations of Phase Transitions in (NH$\text{}_{4}$)$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ Crystal by Means of Mn$\text{}^{2+}$ EPR Spectra
Autorzy:
Bednarski, W.
Waplak, S.
Powiązania:
https://bibliotekanauki.pl/articles/1952756.pdf
Data publikacji:
1996-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.50.-f
76.30.-v
Opis:
EPR of Mn$\text{}^{2+}$ impurity ion in the (NH$\text{}_{4}$)$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ crystal is studied in the temperature range 80-420 K. It is shown that Mn$\text{}^{2+}$ substitutes NH$\text{}_{4}^{+}$(I) ion and is coordinated in deformed oxygen octahedron in which takes two "off-center" positions. Its spin-Hamiltonian parameters and direction cosines of crystal field are determined. The successive EPR line splitting for three phase transitions is discussed.
Źródło:
Acta Physica Polonica A; 1996, 90, 6; 1185-1192
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase-Locked Particle Image Velocimetry Visualization of the Sound Field at the Outlet of a Circular Tube
Autorzy:
Weyna, S.
Mickiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1196700.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.58.+z
43.28.Js
43.25.-x
47.35.Rs
Opis:
The shedding process and acoustic flow formation in the region of outlet of a cylinder duct has been investigated by means of the particle image velocimetry (PIV) technique. The research work on the behavior of the sound field at outlets of waveguides addresses issues of importance to industrial applications. The obtained results can be used in a number of industrial applications involving pipes, ducts and tubing. In our investigation the acoustics flow fields are measured with a phase-locked PIV system with high sampling rate and large internal memory block using DAVIS v. 8.11 software. A cross-correlation method, in conjunction with the FFT analysis, is used as a vector processing algorithm. A series of PIV vector maps was used to evaluate the acoustic velocity field at the open end of circular tube throughout the acoustic cycle for frequencies of 700 Hz and 1400 Hz. Six phase steps were assumed for one frequency cycle and the characteristic signal was extracted from the velocity data step and shown graphically.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-108-A-112
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Diagrams of the Extended Hubbard Model with Repulsive Pair-Hopping Interaction for Nonfrustrated 2D Lattice
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1385232.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We analyze the extended Hubbard model with pair-hopping interaction J, i.e. the Penson-Kolb-Hubbard model, in the case of repulsive J (J < 0) within the (broken symmetry) Hartree-Fock approximation. We focus our study on the effects of on-site U interaction on the mutual stability of magnetic, charge-ordered, and superconducting states including the eta-pairing phase, i.e. the state with the Cooper-pair center-of-mass momentum q=Q. The ground state phase diagrams are obtained for arbitrary particle concentration n on nonfrustrated d=2 square lattice.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 275-277
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Properties of the Penson-Kolb-Hubbard Model with Attractive Pair-Hopping Interaction
Autorzy:
Czart, W.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1385235.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.20.Mn
Opis:
We study the ground state phase diagrams of the extended Hubbard model with the pair-hopping interaction J, i.e. the Penson-Kolb-Hubbard model. We concentrate on the case of attractive J (J > 0) which can stabilise s-wave pairing superconductivity in the system and competes with the on-site repulsive U. The evolution of the phase diagrams and order parameters for arbitrary electron density and representative values of the interaction parameters are analyzed within the (broken symmetry) Hartree-Fock approximation. The calculations are performed for the case of nearest-neighbors electron hopping t on the d=2 square lattice.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 278-280
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting Characteristics of the Penson-Kolb Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2012898.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
We study superconducting properties of the Penson-Kolb model, i.e. the tight-binding model with the pair-hopping (intersite charge exchange) interaction J. The evolution of the critical fields, the coherence length, the Ginzburg ratio, and the London penetration depth with particle concentration n and pairing strength are determined. The results are compared with those found earlier for the attractive Hubbard model.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 217-220
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting Properties of theη-Pairing State in the Penson-Kolb-Hubbard Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2041460.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
The Penson-Kolb-Hubbard model, i.e. the Hubbard model with the pair-hopping interaction J is studied. We focus on the properties of the superconducting state with the Cooper-pair center-of-mass momentum q= Q (η-phase). The transition into theη-phase, which is favorized by the repulsive J (J<0) is found to occur only above some critical value |J$\text{}_{c}$|, dependent on band filling, on-site interaction U and band structure, and the system never exhibits standard BCS-like features. This is in obvious contrast with the properties of the isotropic s-wave state, stabilized by the attractive J and attractive U, which exhibit at T=0 a smooth crossover from the BCS-like limit to that of tightly bound pairs with increasing pairing strength.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 709-713
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity of the Two-Dimensional Penson-Kolb Model
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2029270.pdf
Data publikacji:
2001-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
74.25.Ha
Opis:
Two-dimensional (d=2) Penson-Kolb model, i.e. the tight-binding model with the pair-hopping (intersite charge exchange) interaction, is considered and the effects of phase fluctuations on the s-wave superconductivity of this system are discussed within the Kosterlitz-Thouless scenario. The London penetration depth λ at T=0, the Kosterlitz-Thouless critical temperature T$\text{}_{c}$, and the Hartree-Fock approximation critical temperature T$\text{}_{p}$ are determined as a function of particle concentration and interaction. The Uemura type plots (T$\text{}_{c}$ vs.λ$\text{}^{-2}$(0)) are derived. Beyond weak coupling and for low concentrations they show the existence of universal scaling: T$\text{}_{c}$ ~1/λ$\text{}^{2}$(0), as it was previously found for the attractive Hubbard model and for the models with intersite electron pairing.
Źródło:
Acta Physica Polonica A; 2001, 100, 6; 885-895
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Radiation Induced Spin Photocurrents in Non-Magnetic Low Dimensional Structures
Autorzy:
Ganichev, S. D.
Prettl, W.
Powiązania:
https://bibliotekanauki.pl/articles/2043707.pdf
Data publikacji:
2005-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.40.+w
72.25.Fe
78.67.-n
73.21.Fg
Opis:
Spin photocurrents generated by homogeneous excitation with terahertz radiation in low dimensional structures are reviewed. Three microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a quantum well, the circular photogalvanic effect, the spin-galvanic effect and the magneto-gyrotropic effect. These phenomena provide several methods to investigate various spin properties in low dimensional structures like details of band structure and spin relaxation time.
Źródło:
Acta Physica Polonica A; 2005, 108, 4; 581-608
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Orderings of Half-Filled Extended Hubbard Models with Spin- and Charge-Exchange Interaction
Autorzy:
Czart, W. R.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/2046752.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
75.10.-b
75.30.Gw
71.45.Lr
74.20.-z
Opis:
The electron orderings of the half-filled extended Hubbard models (i) with anisotropic spin-exchange interactions (the t-U-J$\text{}_{ǁ}$-J$\text{}_{⊥}$ model) and (ii) with charge-exchange interaction (the t-U-I model) are discussed. In particular, we present new results concerning the phase diagrams of the model (i) in the case of uniaxial spin exchange (J$\text{}_{ǁ}$≢0) for d-dimensional hypercubic lattices (1≤d≤∞) and conclude about the basic effects of the particular spin- and charge-exchange interaction terms (J$\text{}_{ǁ}$, J$\text{}_{⊥}$, and I) in both models.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 577-582
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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