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Wyświetlanie 1-15 z 15
Tytuł:
Elastic Scattering in Kane Type Semiconductor Circular Dots
Autorzy:
Babanlı, A.
Artunç, E.
Kasalak, T.
Powiązania:
https://bibliotekanauki.pl/articles/1399171.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.22.Pr
73.20.D-
Opis:
In this paper we have investigated the scattering of electrons by a circular narrow penetrable δ-type potential barrier in $A^{3}B^{5}$ type semiconductors by using three-band Kane model. By using the Kane equations with the continuous conditions of the wave functions and flux discontinuous at the interface of two circular dots, we have analytically calculated the total cross-section and the Boltzmann conductivity for the semiconductor quantum rings with delta potential barrier. It has been shown that the quasi-bound states appear as peaks in the cross-section.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 811-814
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetotransport through Nanoconstriction in Ferromagnetic Semiconductor (Ga,Mn)As
Autorzy:
Figielski, T.
Wosiński, T.
Pelya, O.
Sadowski, J.
Morawski, A.
Mąkosa, A.
Dobrowolski, W.
Jagielski, J.
Wróbel, J.
Powiązania:
https://bibliotekanauki.pl/articles/2035752.pdf
Data publikacji:
2003-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.63.-b
75.60.-d
73.20.Fz
Opis:
We studied narrow (submicron) constrictions in the layers of ferromagnetic semiconductor (Ga,Mn)As. We have demonstrated a contribution of the quantum localization effects to the magnetoresistance of the constricted samples. We have also found a negative contribution of a domain wall trapped in the constriction to the resistance, due presumably to the erasing of the localization effects by the domain wall.
Źródło:
Acta Physica Polonica A; 2003, 103, 6; 525-531
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physics of THz Field-Effect Transistors
Autorzy:
Łusakowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1505463.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Mf
52.75.-d
Opis:
Field-effect transistors are nowadays considered as possible elements of THz detection and emission systems. Their THz performance is governed by excitations of two-dimensional plasma in the transistor channel. The paper discusses peculiarities of the photon-plasmon coupling mechanism in field-effect transistors and puts it in the perspective of classical investigation of plasma excitations in two-dimensional systems.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 114-116
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Role of Correlations and Off-Diagonal Terms in Binary Disordered One-Dimensional Systems
Autorzy:
Kosior, A.
Major, J.
Płodzień, M.
Zakrzewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1189984.pdf
Data publikacji:
2015-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
67.85.-d
03.75.-b
73.20.Fz
73.20.Jc
Opis:
We investigate one-dimensional tight binding model in the presence of a correlated binary disorder. The disorder is due to the interaction of particles with heavy immobile other species. Off-diagonal disorder is created by means of a fast periodic modulation of interspecies interaction. The method based on transfer matrix techniques allows us to calculate the energies of extended modes in the correlated binary disorder. We focus on N-mer correlations and regain known results for the case of purely diagonal disorder. For off-diagonal disorder we find resonant energies. We discuss ambiguous properties of those states and compare analytical results with numerical calculations. Separately we describe a special case of the dual random dimer model.
Źródło:
Acta Physica Polonica A; 2015, 128, 6; 1002-1007
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
From Weak to Strong Coupling Superconductivity: Collective Modes in a Model with Local Attraction
Autorzy:
Kostyrko, T.
Micnas, R.
Powiązania:
https://bibliotekanauki.pl/articles/1929358.pdf
Data publikacji:
1993-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
71.28.+d
73.20.Mf
Opis:
We discuss the density-density response functions and the collective excitation spectrum for the extended Hubbard model with on-site attraction and arbitrary electron density, in the superconducting ground state. For the short-range intersite interaction we find the sound wave-like modes with the velocity interpolating smoothly between the weak (v ∝ 2Zt, |U| ≪ 2Zt) and strong coupling (v ∝ Zt$\text{}^{2}$/|U|,|U| ≫ 2Zt) limits. The latter agrees with the results obtained from an effective pseudospin Hamiltonian valid in the strong coupling limit. In the weak coupling regime, we obtain that apart from a commensurate charge density wave instability, an increase in the intersite Coulomb repulsion can give rise to a charge density wave incommensurate with the lattice period, away from half-filling. The ground state phase diagram for 2D square lattice, including singlet superconducting ground state, electronic droplet formation, and charge density waves is determined. It is also shown that the energy of collective excitations evolves smoothly from weak to strong coupling limit for a 2D lattice, in the case of a long-range Coulomb interaction. Finally, the mode coupling effects in the frequency behavior of the density-density response functions are analyzed.
Źródło:
Acta Physica Polonica A; 1993, 83, 6; 837-848
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unzipped and Defective Nanotubes: Rolling up Graphene and Unrolling Tubes
Autorzy:
Chico, L.
Santos, H.
Ayuela, A.
Jaskólski, W.
Pelc, M.
Brey, L.
Powiązania:
https://bibliotekanauki.pl/articles/1535883.pdf
Data publikacji:
2010-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.U-
73.20.-r
73.63.Fg
85.75.-d
Opis:
The properties of carbon nanotubes can be dramatically altered by the presence of defects. In this work we address the properties of two different kinds of defective nanotubes: junctions of achiral tubes with topological defects and partially unzipped carbon nanotubes. In particular, we begin by focussing on the interface states in carbon nanotube junctions between achiral tubes. We show that their number and energies can be derived by applying the Born-von Karman boundary condition to an interface between armchair- and zigzag-terminated semi-infinite graphene layers. We show that these interface states, which were thought to be due to the presence of topological defects, are in fact related to the graphene zigzag edge states. Secondly, we study partially unzipped carbon nanotubes, which can be considered as the junction of a carbon nanotube and a graphene nanoribbon, which has edge features giving rise to novel properties. Carbon nanoribbons act as transparent contacts for nanotubes and viceversa, yielding a high conductance. At certain energies, nanoribbons behave as valley filters for carbon nanotubes; this holds considering electron-electron interaction effects. Furthermore, the application of a magnetic field turns the system conducting, with a 100% magnetoresistance. These novel structures may open a way for new carbon-based devices.
Źródło:
Acta Physica Polonica A; 2010, 118, 3; 433-441
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Orbit Coupling in n-Type PbTe/PbEuTe Quantum Wells
Autorzy:
Peres, M. L.
Chitta, V. A.
Maude, D. K.
Oliveira, N. F.
Rappl, P. H. O.
Ueta, A. Y.
Abramof, E.
Powiązania:
https://bibliotekanauki.pl/articles/2047927.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
72.25.Rb
73.20.Fz
73.63.Hs
Opis:
Magnetoresistance measurements were performed on an n-type PbTe/PbEuTe quantum well and weak antilocalization effects were observed. This indicates the presence of spin-orbit coupling phenomena and we showed that the Rashba effect is the main mechanism responsible for this spin-orbit coupling. Using the model developed by Iordanskii et al., we fitted the experimental curves and obtained the inelastic and spin-orbit scattering times. Thus we could compare the zero field energy spin-splitting predicted by the Rashba theory with the energy spin-splitting obtained from the analysis of the experimental curves. The final result confirms the theoretical prediction of strong Rashba effect on IV-VI based quantum wells.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 602-605
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:
Fermions and Bosons in a Double-Well Potential
Autorzy:
Bielas, A.
Maśka, M.
Powiązania:
https://bibliotekanauki.pl/articles/1374101.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
67.85.-d
67.85.Pq
73.20.Jc
Opis:
The boson-fermion model, describing a mixture of fermions and bosons is analyzed on a small, two-site lattice. The model includes all the on-site Coulomb-type interactions between bosons, between fermions and between fermions and bosons. Additionally, the Hamiltonian includes a term that describes a conversion of a pair of opposite-spin fermions into a boson and vice versa. We show how this conversion depends on the model parameters.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-118-A-122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Potential Investigations of Indium Phosphate Real Surfaces by Means of Transverse Acoustoelectric Method
Autorzy:
Pustelny, T.
Powiązania:
https://bibliotekanauki.pl/articles/1943942.pdf
Data publikacji:
1995-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.-r
43.35.+d
72.50.+b
Opis:
A method of surface potential determination in semiconductors by means of the transverse acoustoelectric effect is described. The results of theoretical analysis of the transverse acoustoelectric voltage versus surface potential and different surface electrical parameters in indium phosphate single crystals are presented. The experimental results of the surface potential investigations have been obtained after various surface treatments in InP(110) and InP(100) crystals. A strong influence of the chemical and mechanical surface treatments upon the surface potential values has been observed from the measurements. The surface InP(110) was more sensitive to different surface treatments. The changes of the surface potential values were about two times greater for InP(110) than for InP(100) samples. The surface potentials after surface treatments obtained by the acoustics method were of the range -0.08 [V] to -0.22 [V].
Źródło:
Acta Physica Polonica A; 1995, 88, 6; 1123-1132
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scanning Tunneling Spectroscopy Study of Surface States of 3d Metals: Chemical Identification, Magnetic Contrast and Orbital Kondo Resonance States
Autorzy:
Bischoff, M. M. J.
Fang, C. M.
de Groot, R. A.
Heijnen, G. M. M.
Katsnelson, M. I.
Kolesnychenko, O. Yu.
de Kort, R.
Lichtenstein, A. I.
Quinn, A. J.
Vasquez de Parma, A. L.
Yamada, T. K.
van Kempen, H.
Powiązania:
https://bibliotekanauki.pl/articles/2036891.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.-r
68.37.-d
75.70.-i
Opis:
The surface states of 3d transition metals are studied by scanning tunneling microscopy and scanning tunneling spectroscopy. The results show that surface states can be used for chemical identification with high spatial resolution. The spin polarized nature of the surface states allows us to obtain magnetic contrast in scanning tunneling miroscopy imaging with near atomic resolution. For Cr(100) we found that the surface state close to the Fermi level can be explained by an orbital Kondo resonance surface state.
Źródło:
Acta Physica Polonica A; 2003, 104, 3-4; 231-243
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monte Carlo Studies of Quantum Cascade Lasers
Autorzy:
Borowik, P.
Thobel, J.
Bugajski, M.
Adamowicz, L.
Powiązania:
https://bibliotekanauki.pl/articles/1807675.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
72.20.Jv
73.63.-b
78.67.-n
Opis:
Results of multi particle Monte Carlo studies of a mid-infrared QCL structure, for the first time fabricated by Page et al., are presented. It has been demonstrated that for the considered structure design at least 9 electron energy levels per laser segment should be used to correctly describe the electric current properties. Mechanisms responsible for electron population on higher laser level are discussed.
Źródło:
Acta Physica Polonica A; 2009, 116, S; S-49-S-51
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Chemical Composition of Liquid Phase and Growth Process on Physical Properties of $Bi_2Se_3,$ $Bi_2Te_3$ and $Bi_2Te_2Se$ Compounds
Autorzy:
Hruban, A.
Materna, A.
Dalecki, W.
Strzelecka, G.
Piersa, M.
Jurkiewicz-Wegner, E.
Diduszko, R.
Romaniec, M.
Orłowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1492965.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
72.10.-d
72.15.-v
72.20.-I
73.20.-r
Opis:
We studied synthesis and crystal growth of $Bi_2Te_3,$ $Bi_2Se_3$ and $Bi_2Te_2Se$ compounds by means of vertical Bridgman method. Crystals were grown from stoichiometric melts and under different molar ratio of Bi:Te, Bi:Se or Bi:Te:Se. The obtained crystals were characterized by X-ray diffraction analysis, energy dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy, and the Hall effect measurements. Some of the samples demonstrated insulating bulk behavior, by means of resistivity versus temperature measurements.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 950-953
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Silver Nanoparticles as Enhancing Substrates for Raman and Fluorescence Spectroscopy
Autorzy:
Cyrankiewicz, M.
Wybranowski, T.
Kruszewski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1196708.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.20.Fb
33.20.Kf
32.50.+d
61.46.Df
73.20.Mf
78.67.Bf
87.83.+a
Opis:
The enhancing properties of silver nanoparticles in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF) are studied in this work. The obtained results confirm that the partial aggregation of nanoparticles leads to a great increase of Raman scattering cross-section but there are significant differences in SERS-activity of colloidal silver treated with various aggregating compounds. The differences are interpreted through the analysis of both experimental and computational results. The same silver colloid covered with silica shell preventing the fluorescence quenching makes possible a several-fold increase in fluorescence emission. The effect strongly depends on thickness of the outer layer of nanoparticles. Geometrical parameters of nanoparticles (radius or radius and thickness of the adsorption layer in core-shell systems) are determined on the basis of the dynamic light scattering (DLS) data and extinction spectra analysis.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-11-A-15
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Correlations within Fermionic Lattice Models
Autorzy:
Matlak, M.
Grabiec, B.
Krawiec, S.
Powiązania:
https://bibliotekanauki.pl/articles/2047738.pdf
Data publikacji:
2007-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.-w
71.10.Ca
71.10.Fd
71.20.Be
71.27.+a
71.28.+d
73.21.La
78.67.Bf
Opis:
We investigate two-site electronic correlations within generalized Hubbard model, which incorporates the conventional Hubbard model (parameters: t (hopping between nearest neighbours), U (Coulomb repulsion (attraction))) supplemented by the intersite Coulomb interactions (parameters: J$\text{}^{(1)}$ (parallel spins), J$\text{}^{(2)}$ (antiparallel spins)) and the hopping of the intrasite Cooper pairs (parameter: V). As a first step we find the eigenvalues E$\text{}_{α}$ and eigenvectors |E$\text{}_{α}$〉 of the dimer and we represent each partial Hamiltonian E$\text{}_{α}$|E $\text{}_{α}$〉〈 E$\text{}_{α}$| (α=1,2,...,16) in the second quantization with the use of the Hubbard and spin operators. Each dimer energy level possesses its own Hamiltonian describing different two-site interactions which can be active only in the case when the level will be occupied by the electrons. A typical feature is the appearance of two generalized t-J interactions ascribed to two different energy levels which do not vanish even for U=J$\text{}^{(1)}$=J{(2)}=V=0 and their coupling constants are equal to ±t in this case. In the large linebreak U-limit for J$\text{}^{(1)}$=J$\text{}^{(2)}$=V=0 there is only one t-J interaction with coupling constant equal to 4t$\text{}^{2}$/|U| as in the case of a real lattice. The competition between ferromagnetism, antiferromagnetism and superconductivity (intrasite and intersite pairings) is also a typical feature of the model because it persists in the case U=J$\text{}^{(1)}$=J$\text{}^{(2)}$=V=0 and t≢0. The same types of the electronic, competitive interactions are scattered between different energy levels and therefore their thermodynamical activities are dependent on the occupation of these levels. It qualitatively explains the origin of the phase diagram of the model. We consider also a real lattice as a set of interacting dimers to show that the competition between magnetism and superconductivity seems to be universal for fermionic lattice models.
Źródło:
Acta Physica Polonica A; 2007, 112, 3; 537-547
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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