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Tytuł:
The Influence of Lattice Defects on the Ground-State Properties of the Falicov-Kimball Model in Two Dimensions
Autorzy:
Žonda, M.
Farkašovský, P.
Čenčariková, H.
Powiązania:
https://bibliotekanauki.pl/articles/1813656.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.27.+a
71.28.+d
71.30.+h
Opis:
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 $Sm_{1-x}B_6$.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 291-294
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamics of the Generalized Spin-One-Half Falicov-Kimball Model in Two Dimensions
Autorzy:
Žonda, M.
Farkašovský, P.
Čenčariková, H.
Powiązania:
https://bibliotekanauki.pl/articles/1810315.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.27.+a
71.28.+d
Opis:
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.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 104-106
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure Induced Transitions in Heavy-Fermion Systems footnotemark
Autorzy:
Zhang, Sun
Dong, Yi-Qiao
Powiązania:
https://bibliotekanauki.pl/articles/1401900.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Mb
75.20.Hr
71.28.+d
74.62.Fj
Opis:
In this paper, the electron-type heavy-fermion system and the hole-type heavy-fermion system are classified by means of the cell-volume difference between two typical valence states of f ions. Two kinds of transitions induced by pressure are studied theoretically within a unified picture presented for both two types of heavy-fermion systems. Among these transitions, the incoherence-to-coherence transition in the electron-type heavy-fermion system is confirmed intensively in experiments, while the coherence-to-incoherence transition in the hole-type heavy-fermion system is discussed as a prediction for further observations.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 389-393
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Dynamics in Crystalline Semiconductors
Autorzy:
Zawadzki, W.
Powiązania:
https://bibliotekanauki.pl/articles/1400405.pdf
Data publikacji:
2013-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
73.61.Ey
72.20.-i
Opis:
Electron dynamics in crystalline semiconductors is described by distinguishing between an instantaneous velocity related to electron's momentum and an average velocity related to its quasi-momentum in a periodic potential. It is shown that the electron velocity used in the theory of electron transport and free-carrier optics is the average electron velocity, not the instantaneous velocity. An effective mass of charge carriers in solids is considered and it is demonstrated that, in contrast to the "acceleration" mass introduced in textbooks, it is a "velocity" mass relating carrier velocity to its quasi-momentum that is a much more useful physical quantity. Among other advantages, the velocity mass is a scalar for spherical but nonparabolic energy bands ϵ(k), whereas the acceleration mass is not a scalar. Important applications of the velocity mass are indicated. A two-band k·p^ model is introduced as the simplest example of a band structure that still keeps track of the periodic lattice potential. It is remarked that the two-band model, adequately describing narrow-gap semiconductors (including zero-gap graphene), strongly resembles the special theory of relativity. Instructive examples of the "semi-relativistic" analogy are given. The presentation has both scientific and pedagogical aspects.
Źródło:
Acta Physica Polonica A; 2013, 123, 1; 132-138
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
2D Angular Correlation of Annihilation Radiation: Current Trends and Future Possibilities
Autorzy:
West, R. N.
Powiązania:
https://bibliotekanauki.pl/articles/1933550.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
71.25.Ηc
78.70.Bj
Opis:
Recent improvements in two-dimensional angular correlation measurement and analysis techniques have greatly increased the power of the method to image the Fermi surfaces of electronically complex systems. That, and the further and dramatic improvement that must result when the present radioisotope positron sources are replaced by intense monoenergetic positron beams are discussed and illustrated.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 249-256
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybridization Effects in UCu$\text{}_{5-x}$Au$\text{}_{x}$ Compounds
Autorzy:
Tran, V. H.
Troć, R.
Powiązania:
https://bibliotekanauki.pl/articles/1929857.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
Opis:
We review the results of bulk and neutron diffraction measurements on the UCu$\text{}_{5-x}$Au$\text{}_{x}$ system crystallizing in the cubic AuBe$\text{}_{5}$-type structure. The observed properties may be understood in the light of competition between Kondo effect and RKKY exchange interactions. Effects of 5f-ligand hybridization between the U-atoms occupying the 4a-sites and the Au- or/and Cu-atoms placed at the 4c- and 16e-positions, respectively, are supposed to be different. We show that the prefential occupation of 4c-sites by Au has a marked effect on the magnetic properties of the investigated system.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 287-292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Far-Infrared Study of DX-Like Centers in Pb$\text{}_{0.95}$Mn$\text{}_{0.05}$Te(Ga)
Autorzy:
Stojanović, D.
Trajić, J.
Hadžić, B.
Romčević, M.
Ivanchik, I. I.
Khokhlov, D. R.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/2047857.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
78.20.-e
63.20.Pw
Opis:
We present far-infrared reflection spectra of Pb$\text{}_{0.95}$Mn$\text{}_{0.05}$Te single crystal doped with gallium between 10 and 300 K. The analysis of the far-infrared reflection spectra was made by a fitting procedure based on the model of coupled oscillators. Together with the strong plasmon-phonon coupling we obtain three local modes of gallium at about 122 cm$\text{}^{-1}$, 166 cm$\text{}^{-1}$, and 192 cm$\text{}^{-1}$. The position of these modes depends on impurity center charge, and their intensity depends on temperature.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 959-962
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exchange Interaction as a Source of Real Space Pairing in High Temperature Superconductors and Heavy Fermions: a Brief Overview
Autorzy:
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1860823.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
75.10.Lp
74.70.Vy
Opis:
We characterize the principal difference between the pairing induced by the kinetic exchange interactions for the Fermi-liquid and spin-liquid phases. In the case of hybridized electrons the Kondo-exchange induced pairing is invoked, whereas for a single narrow-band case kinetic exchange is responsible for the spin singlet pairing. The former interaction is applied to heavy-fermion systems, whereas the latter is employed to the high temperature superconductors. The current situation concerning the applicability of our theoretical models is briefly and critically assessed.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 39-52
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strongly Correlated Electrons in a Magnetic Field: Fermi Liquid versus Spin Liquid
Autorzy:
Spałek, J.
Wójcik, W.
Powiązania:
https://bibliotekanauki.pl/articles/1930575.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.-d
75.10.Lp
Opis:
We compare the Fermi liquid (FL) and statistical spin liquid (SSL) representations of the electronic properties for strongly correlated systems. In particular, we discuss the entropy, as well as the magnetization as a function of band filling, temperature and magnetic field. These properties are quite different in the two (FL, SSL) states. Antiferromagnetic state disappears for a small number of holes in the doped Mott insulator.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 357-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Spectroscopy of Multiphonon Emission Process in Ni-Doped PbTe
Autorzy:
Romčević, N.
Trajić, J.
Hadžić, B.
Romčević, M.
Stojanović, D.
Lazarević, Z.
Kuznetsova, T.
Khokhlov, D.
Rudolf, R.
Anžel, I.
Powiązania:
https://bibliotekanauki.pl/articles/1807841.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
63.20.-e
78.30.-j
Opis:
In this paper, we present room temperature unpolarized Raman scattering spectra of Ni doped PbTe single crystal sample. Crystal of PbTe(Ni) was grown by the Bridgman method. The Ni concentration in the sample used here was 1× $10^{19}$ at./$cm^{3}$. Well resolved peaks appear at about 126, 143, 181, 362 and 724 $cm^{-1}$. The modes at 126 and 143 $cm^{-1}$, which are also observed in other telluride compounds, originate from vibrations in $TeO_2$. We assume that the mode at about 181 $cm^{-1}$ is connected to excitations of a local phonon mode in the vicinity of an impurity atom (donor $Ni^{3+}$ state). Modes at about 362 $cm^{-1}$ and 724 $cm^{-1}$ are the second and fourth harmonic of a local phonon mode, registered here due to multiphonon emission.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 91-92
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pseudospin Models of Superconductors with Very Short Coherence Length
Autorzy:
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1860991.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
05.30.Jp
71.28.+d
Opis:
We discuss a few models developed for description of superconductivity with very short coherence length and point out their formal equivalence to specific spin models, such as an anisotropic Heisenberg model (s = 1/2) with two- and four-spin exchange coupling and with fixed magnetization in the z-direction, an XY-Z model with single ion anisotropy and a Kondo-lattice model with anisotropic on-site exchange. New results concerning the phase diagram of the Hubbard model with strong attraction, the electromagnetic properties of systems with the first order superconducting transition and a possibility of local charge moment compensation in systems of coexisting bound pairs and itinerant electrons are presented.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 117-131
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity, Charge Orderings and Phase Separations in Systems with Local Electron Pairing
Autorzy:
Robaszkiewicz, S.
Pawłowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1946347.pdf
Data publikacji:
1996-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
05.30.Jp
71.28.+d
Opis:
We study two effective models developed for description of superconductors with short-coherence length: (i) the extended Hubbard model with on-site attraction and intersite repulsion, (ii) the model of hard-core charged bosons on a lattice. The analysis is concentrated on the problem of phase separations and competition between superconductivity (SS) and charge-density-wave (CDW) orderings. The phase diagrams of the systems are shown to consist of at least seven different states, including 3 types of phase separated (PS) states: CDW-SS (PS1), CDW-normal (PS2) and the state of electron droplets (PS3). By taking into account the PS states and the effects of longer-range density-density interactions (beyond nearest neighbors) our paper substantially generalizes and modifies the conclusions of previous papers concerning the models considered.
Źródło:
Acta Physica Polonica A; 1996, 90, 3; 569-586
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Ray Resonant Magnetic Scattering: Application to Thin Films and Multilayers
Autorzy:
Raoux, D.
Jaouen, N.
Tonnerre, J. M.
Bontempi, E.
Powiązania:
https://bibliotekanauki.pl/articles/2014370.pdf
Data publikacji:
2000-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
78.70.Ck
71.27.+a
Opis:
This paper reports on the use of a new technique to investigate the magnetic properties of thin films, multilayers and artificial structures, the X-ray resonant magnetic scattering at small values of the scattering vector. It can be used either by registering the reflectivity pattern or in a diffraction mode. In comparison with magneto-optical Kerr effect or neutron scattering, it offers an atomic selectivity due to the resonant excitation of a core electron, and even an electronic shell one. Examples are presented mainly in the soft X-range allowing to probe the 3d band of transition metals. They demonstrate the promising possibilities of the method to measure the magnetic moments carried by each of the atomic components in complex systems, as well as their distribution through thin layers, with an atomic resolution.
Źródło:
Acta Physica Polonica A; 2000, 98, 5; 483-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
$\text{}^{11}$B-NMR Study of $SmB_6$ under Pressure
Autorzy:
Pristáš, G.
Mito, T.
Kohara, T.
Gabáni, S.
Reiffers, M.
Flachbart, K.
Takeshita, N.
Shitsevalova, N.
Powiązania:
https://bibliotekanauki.pl/articles/1534330.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.60.-k
62.50.-p
71.28.+d
Opis:
We present first experimental results of $\text{}^{11}$B-NMR of SmB_6 under applied pressure. From measurement of nuclear spin-lattice relaxation time $(T_1)$ we find that with applied pressure the value of activation gap $E_{g}$ is decreasing. This decrease is larger than in case of other experimental techniques. We suppose that the enhancement of $1//T_1$ in temperature range 20-100 K with applied pressure reflects not only a suppression of hybridization gap, but also changes in spin correlations.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 895-896
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertex Corrections to the Electrical Conductivity of the Disordered Falicov-Kimball Model
Autorzy:
Pokorný, V.
Janiš, V.
Powiązania:
https://bibliotekanauki.pl/articles/1534607.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
71.28.+d
72.10.Fk
Opis:
Quantum coherence of elastically scattered lattice fermions is studied. We calculate vertex corrections to the electrical conductivity of electrons scattered either on thermally equilibrated or statically distributed random impurities and we demonstrate that the sign of the vertex corrections to the Drude conductivity is in both cases negative.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 922-923
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 45

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