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Wyświetlanie 1-15 z 19
Tytuł:
Shallow-Deep Instability of Donor States in Many-Valley Semiconductors
Autorzy:
Grinberg, M.
Powiązania:
https://bibliotekanauki.pl/articles/1890895.pdf
Data publikacji:
1991-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
71.38.+i
Opis:
The shallow-deep instability of double and single donors in multi-valley semi conductors using the model Hamiltonian is studied. The obtained results describe properly the properties of double donors (in D$\text{}^{0}$ and D$\text{}^{+}$ state) in Ge and single deep donors in Al$\text{}_{x}$Ga$\text{}_{1-x}$As for 0.3 < x < 0.5.
Źródło:
Acta Physica Polonica A; 1991, 80, 3; 361-364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Diagram of Mixed-Stack Compounds with Intermolecular Electron Transfer
Autorzy:
Luty, Tadeusz
Powiązania:
https://bibliotekanauki.pl/articles/1933456.pdf
Data publikacji:
1995-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
71.35.+z
Opis:
The ground state energy for a chain of donor and acceptor molecules (mixed-stack architecture) is calculated within the three-state model. The model describes the intermolecular electron transfer and, in particular, stresses the role of the diagonal coupling of the electron to symmetry breaking molecular displacements and the local electric field. The modulation of the intermolecular Coulomb interaction is shown to have important consequences for the ground state and its dynamics. In particular, the ground state energy as a function of the displacement may show one, two or three minima with varied molecular ionicity. An analysis of the function gives a phase diagram which indicates a possibility for the coexistence of neutral (undistorted) and ionic (distorted) chains of molecules in the ground state. The function is illustrated by numerical calculations with parameters appropriate for the tetrathiafulvalene-chloranil crystal which undergoes a neutral-to-ionic phase transition induced by either temperature or pressure. The effect of the electron transfer on the lattice dynamics of the mixed-stack system is briefly considered. It is suggested that the thermodynamical phase diagram for tetrathiafulvalene-chloranil system can be understood as a result of two effects: pressure induced quantum mixing between diabatic states which determine a nature of components and temperature stimulated classical mixing of the components.
Źródło:
Acta Physica Polonica A; 1995, 87, 6; 1009-1021
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solitons in a One-Dimensional Degenerate Hubbard Model
Autorzy:
Lipiński, S.
Powiązania:
https://bibliotekanauki.pl/articles/1888014.pdf
Data publikacji:
1991-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
71.10.+x
Opis:
An effective magnon-lattice Hamiltonian for the degenerate Hubbard chain with electron-phonon interaction is derived and a formalism for the description of solitary magnons is presented.
Źródło:
Acta Physica Polonica A; 1991, 80, 1; 117-128
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Photomemory Effect in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te$\text{}_{1-y}$Se$\text{}_{y}$:In for Direct Measurements of Magnetization of Bound Magnetic Polarons
Autorzy:
Wojtowicz, T.
Koleśnik, S.
Miotkowski, I.
Furdyna, J. K.
Powiązania:
https://bibliotekanauki.pl/articles/1921550.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
75.50.Pp
Opis:
The first direct measurement of the magnetization of donor bound magnetic polarons in diluted magnetic semiconductors is reported. The experiment has been performed taking advantage of photomemory effect found in n-type Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te$\text{}_{1-y}$Se$\text{}_{y}$ crystals doped with In. Good agreement between experimental results and theory of bound magnetic polarons is observed.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 637-640
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Shallow Donors and Acceptors in GaN; Bound Excitons and Pair Spectra
Autorzy:
Stępniewski, R.
Wysmołek, A.
Powiązania:
https://bibliotekanauki.pl/articles/1946873.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.-y
71.55.Eq
71.38.+i
Opis:
Recent photoluminescence results obtained for homoepitaxial GaN layers are presented. Dominant photoluminescence structures observed for these layers can be assigned to excitons bound to neutral impurities. Different methods such as temperature dependent evolution, high magnetic field and time resolved spectroscopy have been used to study the exciton line properties. For the p-type samples sharp lines are observed, assigned to the donor-acceptor recombination for differently distant pairs. The analysis of the optical transitions related to donors and acceptors is in reasonable agreement with the effective mass approximation. Electron phonon interaction was found to strongly affect the optical properties of GaN. The dominant intrinsic defect has been identified as a donor located at a nitrogen site.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 681-690
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Towards a Unified View of Electron-Phonon Coupling in 1D Solids
Autorzy:
Girlando, A.
Painelli, A.
Soos, Z. G.
Powiązania:
https://bibliotekanauki.pl/articles/1933319.pdf
Data publikacji:
1995-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
71.27.+a
71.45.Lr
Opis:
We analyze the effect of on-site and on-bond electron-phonon (e-ph) coupling in different classes of quasi one-dimensional (1D) solids in terms of a single model. The model was originally developed to account for e-ph coupling in charge transfer crystals and to interpret their vibrational spectra. The same model is extended to conjugated polymers, showing that important information about the electronic structure can be obtained through a careful analysis of vibrational data. Evidence of e-ph coupling in the spectra of halogen-bridged transition-metal complexes is also presented. The unified model thus applies to different classes of 1D systems and yields transferable e-ph coupling constants.
Źródło:
Acta Physica Polonica A; 1995, 87, 4-5; 735-742
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitonic Instabilities of Deformable Lattice - from Self-Trapping to Phase Transition
Autorzy:
Toyozawa, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1931862.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
71.35.+z
71.38.+i
Opis:
The optically created exciton will be self-trapped if its coupling to phonons is strong enough, and will moreover be self-decomposed if the electron and the hole couple to phonons in an opposite way. The bistability between the parity-conserved and parity-broken self-trapped excitons was observed in alkali halides. The situation is most dramatic if the bistability between the parity-broken self-trapped exciton and the ground state (with no exciton) comes into play since the electron-hole pairs may then be spontaneously generated at every lattice site, resulting in the electronic and structural phase transition. The neutral to ionic phase transition observed in a few organic charge transfer compounds under applied pressure or decreasing temperature can be considered as an example. Recent experiment revealed that TTF-chloranil, among others, is subject to photo-induced transient phase change over hundreds of unit cells per one photon. The dynamics of this process can be described in terms of self-trapping and self-multiplication of a photo-generated charge transfer exciton along the chain through the attractive dipolar interaction. This description of phase transition in terms of exciton dynamics will provide a new paradigm of materiology.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 47-56
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Formation of the DX State by Donors in Al$\text{}_{x}$Ga$\text{}_{1-x}$As - Experiment
Autorzy:
Dobaczewski, L.
Kaczor, P.
Missous, M.
Żytkiewicz, Z. R.
Dobosz, D.
Peaker, A. R.
Powiązania:
https://bibliotekanauki.pl/articles/1924251.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
71.55.Eq
78.50.Ge
Opis:
A high-resolution Laplace-transform deep level transient spectroscopy was used to study electron emission from the DX centres related to group IV and VI donor elements in AlGaAs. This provides the experimental evidence that substitutional-interstitial atom motion is responsible for DX behaviour and for the associated metastability effects.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 905-907
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Bound Magnetic Polarons on Magnetic and Electrical Properties in Metallic n-Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se
Autorzy:
Głód, P.
Sawicki, M.
Dietl, T.
Skośkiewicz, T.
Lenard, A.
Plesiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1931936.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.38.+i
75.20.Hr
Opis:
Doping-induced contribution to the millikelvin magnetic susceptibility of Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se:In has been found to undergo a maximum at n ≈ 2n$\text{}_{c}$, and to vanish for n ≥ 8n$\text{}_{c}$, where n$\text{}_{c}$ is the electron concentration corresponding to the metal-insulator transition. This confirms the presence, also in the metallic phase, of bound magnetic polarons. Their slow dynamics may account for hysteresis visible in our magnetoresistance data.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 173-175
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physics of Neutral-to-Ionic Phase Transition in Organic Charge Transfer Semiconducting Compounds
Autorzy:
Cailleau, H.
Lemée-Cailleau, M. H.
Le Cointe, M.
Luty, T.
Powiązania:
https://bibliotekanauki.pl/articles/1967953.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
61.50.Ks
71.35.Aa
Opis:
An uncommon excitonic instability takes place in some exotic semiconducting compounds. Indeed, the equilibrium neutral-to-ionic (N-I) phase transition, as well as the non-equilibrium photo-induced phase transformation, observed in some organic charge-transfer complexes, originate from intra- and inter-chain cooperative effects between structurally relaxed charge-transfer excitations. This electronic-structural phase transition manifests itself by a change of the degree of charge-transfer and a dimerization distortion with the formation of donor-acceptor pairs along the stacking axis in the I phase. Thermal charge-transfer excitations associated with the formation of I strings along N chains are at the heart of the mechanism of this phase transition. These relaxed electronic excitations, which are an intrinsic feature of low-dimensional systems with strong electron-phonon coupling, can be described in terms of self-trapping and self-multiplication of charge-transfer excitons. Precise structural studies on the prototype compound, tetrathiafulvalene-p-chloranil allow to highlight the respective role taken by the ionicity and the dimerization. Symmetry and thermodynamics analysis of the N-I transition, based on recent determination of the pressure-temperature phase diagram, make possible to present a consistent picture of this phase transition. Supported by theoretical considerations taking into account the interplay between quantum and thermal effects, the experimental observations show that the N-I transition results from the condensation and the ordering (crystallization) of charge-transfer excitations, following a phase diagram analogous to the solid-liquid-gas one.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 597-608
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectroscopic Investigations of Charge Transfer Salt VINΦ$\text{}_{2}$(TCNQ)$\text{}_{2}$
Autorzy:
Łapiński, A.
Świetlik, R.
Strzelecka, H.
Veber, M.
Powiązania:
https://bibliotekanauki.pl/articles/1933382.pdf
Data publikacji:
1995-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
78.30.Jw
78.40.-q
Opis:
VINΦ$\text{}_{2}$(TCNQ)$\text{}_{2}$ is a salt with two different, non-parallel TCNQ stacks. The polarized reflectance spectra from single crystals in the IR region 660-5200 cm$\text{}^{-1}$, the powder absorption spectra 400-45000 cm$\text{}^{-1}$ and FT-NIR Raman spectra of VINΦ$\text{}_{2}$(TCNQ)$\text{}_{2}$ are measured at room temperature. Moreover, the temperature dependence of powder absorption spectra in the frequency range 400-7900 cm$\text{}^{-1}$ are studied. The nature of electronic bands, the anisotropy of optical conductivity, the temperature dependence of some vibrational bands and the charge distribution on different TCNQ stacks are discussed.
Źródło:
Acta Physica Polonica A; 1995, 87, 4-5; 835-841
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Anharmonic Polaronic Model
Autorzy:
Konior, J.
Powiązania:
https://bibliotekanauki.pl/articles/1923721.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
74.20.-z
33.10.Cs
Opis:
Anharmonic polaronic model is considered. The model consists of the electronic subsystem, described within the extended Hubbard model, coupled to anharmonic local phonons. By the canonical Holstein-Lang-Firsov transformation the electron-phonon interaction term is ruled out and, then, the effective electronic Hamiltonian is obtained by averaging over the ground state of the phononic subsystem. It is shown that anharmonicity introduces two main additional factors as compared with the harmonic case. First, the band narrowing factor is less rapidly decaying function of the electron-phonon interaction strength. Second, anharmonicity introduces further renormalization of the on- and intersite interaction between fermions.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 773-776
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polaron Effect on the Binding Energy of Shallow Donor in Cylindrical Quantum Dot
Autorzy:
Charrour, R.
Bouhassoune, M.
Bria, D.
Nougaoui, A.
Fliyou, M.
Powiązania:
https://bibliotekanauki.pl/articles/2011186.pdf
Data publikacji:
1999-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
73.20.Dx
73.20.Hb
Opis:
In the framework of the effective-mass approximation and the modified Lee-Low-Pines variational method, we present a theoretical study of the effect of the confined longitudinal-optical phonon and two types of surface-optical phonon (top and side mode) on the binding energy of shallow donor in cylindrical quantum dot. The effect of quantum confinement is described by an infinitely deep potential well. The impact of these different phonon modes is important and depends on the dimension of the quantum dot.
Źródło:
Acta Physica Polonica A; 1999, 96, 6; 759-768
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Polaron Scenario for High-T$\text{}_{c}$ Superconductivity
Autorzy:
Ranninger, J.
Powiązania:
https://bibliotekanauki.pl/articles/1860957.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.+z
71.38.+i
67.20.+k
Opis:
On the basis of experimental evidence we conclude that high-T$\text{}_{c}$ superconducting materials are composed of two distinct subsystems: one in which electrons are bound together in form of localized pairs of small polarons (bipolarons) and one in which electrons exist as strongly correlated Fermions. Upon doping one passes at a critical doping rate from the insulating parent compounds to metallic compounds. There, a charge transfer mechanism between the two subsystems sets in abruptly by which bipolarons can decay into pairs of electrons and vice versa. Such a picture can be modelled by a mixture of interacting Bosons and Fermions. A superconducting ground state for such a system develops at low temperature which is characterized by the opening of a gap in the single electron spectrum and the appearance of collective Boson excitations with a linear spectrum which is confined to the energy regime of the gap. Above T$\text{}_{c}$, a pseudo-gap remains upon closing the superconducting gap. There are strong indications that the normal state has non Fermi liquid behaviour.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 89-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polaron Problem in Quantum Wells
Autorzy:
Bardyszewski, W.
Prywata, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934053.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
71.38.+i
73.20.Dx
Opis:
The effect of polar interaction between an electron in a quantum well and bulk longitudinal optical phonons is analysed. Electron spectral density function is calculated in the lowest order cumulant approximation. The position and linewidth of the quasiparticle peak are obtained as a function of quantum well width and temperature.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 969-973
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 19

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