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1
Content available remote

Impurity Self-Screening

100%
Wilamowski Z., Przybylińska H.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
832-834
EN
In a mixed valence impurity system the distribution of impurity charges can be adjusted to minimize the Coulomb energy of inter-impurity interactions. In this paper we discuss the possibility of extending the methods of analytical evaluation of the pair correlation function for classical liquids to apply to a system with a built-in disorder, where the occupation probability is governed by the Fermi-Dirac statistics.
2
Content available remote

Interplay of Quantum Size Effect and Surface Electron Scattering in Conductivity of Thin Films

100%
Makarov N. M., Moroz A. V.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
457-460
EN
We constructed the most general theory of the classical and quantum static electron transport for 3D films with randomly rough boundaries. The electron-surface interaction was included via approximation with mildly sloping asperities, when the rms height ξ of boundary defects is less than their mean length L. Then we analyzed influence of spatial quantization and electron-surface scattering on the film conductivity ⟨σ⟩ and their interference. Joint action of those factors leads to peculiarities (sharp dips) of ⟨σ⟩ versus the sample thickness d appearing at points where a new conducting electron channel opens. The dips have fundamental quantum origin and are caused by size quantization of electron-surface scattering rate. When studying ⟨σ⟩ versus the bulk mean free path l of electrons, we revealed that, as bulk collisions vanish (l → ∞), the quantum conductivity approaches finite residual value associated with electron-surface interaction. The residual conductivity was first shown to possess either quantum or exclusively classical origin depending on d, l, and the electron wavelength. On the basis of the investigations provided, the relation between quantum and classical effects in the film conductivity was clarified. The theoretical results were successfully tested against recent experimental data concerning the conductivity of ultrathin films.
3
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Bulk and Epitaxial Co_2MnSi Systems with Antisite Disorder: Ab Initio Calculations

100%
Carva K., Turek I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
183-186
EN
The intermetallic compound Co_2MnSi is halfmetallic, but the structure of real samples is often affected by antisite disorder. The influence of disorder on transport properties is examined by ab initio calculations and is found to be more significant in thin Co_2MnSi slabs sandwiched by metallic leads than in the bulk compound.
4
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Determination of Inelastic Mean Free Path of Electrons in Noble Metals

100%
Doliński W., Mróz S., Palczyński J., Gruzza B., Bondot P., Porte A.
Acta Physica Polonica A
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1992
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vol. 81
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issue 2
193-199
EN
The experimental values of Inelastic Mean Free Path (λ_{IMFP}) of electrons in noble metals (Ag, Au, Cu) are determined in the electron energy range 150-2000 eV. The method used consists of the measurements and theoretical calculations of the coefficient of elastic backscattering of electrons from a solid surface η_{e}. The obtained values of λ_{IMFP} are compared with the data available in the literature.
5
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Conduction Mechanism of 4-Aminoantipyrine as a New Organic Semiconductor

80%
Yahia I.
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vol. 125
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issue 5
1167-1171
EN
X-ray diffraction pattern of 4-aminoantipyrine was studied and it is a single phase with a polycrystalline structure. 4-aminoantipyrine has hexagonal structure with space group P6/mcc. The electrical properties of 4-aminoantipyrine were studied in the temperature range (303-373 K) below the melting point of the studied compound and in the frequency range (100 Hz-100 kHz). The obtained results of dc conductivity showed a positive temperature coefficient at the lower temperatures and a negative temperature coefficient at the higher temperatures. The ac conductivity obeys the power law. Ac conductivity can be reasonably interpreted in terms of overlapping-large polaron tunneling model and the correlated barrier hopping model. 4-aminoantipyrine is a good candidate for electronic device due to its electrical conductivity and capacitance.
6
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The Magnetic Equation of State and Transport Properties in Reduced Dimensions

80%
Warda K., Wojtczak L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
878-880
EN
Basing our considerations on magnetic equation of state applied to the description of magnetic systems of confined geometry we developed the model of calculations of the electrical resistivity for metallic multilayers. It was shown that in the transport of charge in ferromagnetic material d-electrons play an important role. The key parameters in the presented model are: the width of the electron energy band and the shift of the energy level for two spin orientations as well as the Fermi energy and size of the sample (the thickness of magnetic and nonmagnetic layers and the total number of layers). The presented results of calculations for temperature dependence of magnetoresistance are in qualitative agreement with the available experimental data. The model calculations introduced in this paper can be applied to current-in-plane geometry as well as to current-perpendicular-to-plane geometry. The calculations are valid within the limitations of the resistor network model.
7
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Optical and Electrical Studies of Graphene Deposited on GaN Nanowires

80%
Kierdaszuk J., Kaźmierczak P., Drabińska A., Wysmołek A., Korona K., Kamińska M., Pakuła K., Pasternak I., Krajewska A., Żytkiewicz Z.
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vol. 126
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issue 5
1087-1089
EN
In this paper using scanning electron microscope, contactless microwave electronic transport and the Raman spectroscopy we studied the properties of graphene deposited on GaN nanowires and compared it with the graphene deposited on GaN epilayer. The Raman micro-mapping showed that nanowires locally change the strain and the concentration of carriers in graphene. Additionally we observed that nanowires increase the intensity of the Raman spectra by more than one order of magnitude.
8
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Pressure Study of Charged Donor Ordering in HgSe Doped with Iron and Gallium

80%
Skierbiszewski C., Suski T., Kossut J., Wilamowski Z., Dobrowolski W., Witkowska B.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
401-404
EN
Transport experiments (Hall effect and conductivity) under hydrostatic pressure up to 1 GPa at liquid helium temperatures on HgSe: Fe, Ga (N_{Fe} = 2 x 10^{19} cm^{-3}; 0 ≤ N_{Ga} ≤ 10^{19} cm^{-3}) were performed. The results show that the gallium co-doping of HgSe:Fe decreases the degree of spatial correlations between charged impurities. Under the hydrostatic pressure, used as a tool for changing the ratio of the charged to neutral impurities, this effect is even more pronounced. A qualitative agreement between the calculation within the short-range correlation model and our experimental data is achieved.
9
Publication available in full text mode
Content available

Anderson Localization of Electromagnetic Waves in Dielectric Media: Model Studies

80%
Rusek M., Orłowski A.
Acta Physica Polonica A
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2006
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vol. 109
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issue 1
109-119
EN
Anderson localization of electromagnetic waves in random arrays of dielectric cylinders confined within a planar metallic waveguide is studied. The disordered dielectric medium is modeled by a system of randomly distributed 2D electric dipoles. An effective theoretical approach based on the method of images is developed. A clear distinction between isolated localized waves (which exist in finite media) and the band of localized waves (which appears only in the limit of the infinite medium) is presented. The Anderson transition emerging in the limit of an infinite medium is observed both in finite size scaling analysis of transmission and in the properties of the spectra of some random matrices. The sound physical interpretation of the obtained results suggests deeper insight into the existing experimental and theoretical work.
10
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Electron Scattering and the Band Structure of Mixed Crystals Hg_{1-x}Fe_{x}Se

80%
Skierbiszewski C., Wilamowski Z., Suski T., Kossut J., Witkowska B.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
809-812
EN
In this paper the dependence of the band structure and the electron scattering mechanisms on the molar fraction x are studied in Hg_{1-x}Fe_{x}Se. The crossover from the zero-gap band to the open band-gap configuration at x ≈ 0.08 is predicted. We explain the drop of the electron mobility for x > 0.002 by the alloy scattering mechanism.
11
Content available remote

Transport Properties of Rippled Graphene

80%
Zwierzycki M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1246-1249
EN
It is common to describe graphene as ideally flat plane, however there exists both theoretical and experimental evidence that it is most usual to find it in a rippled state. The ripples can be either induced by the substrate or formed spontaneously in suspended graphene. The lateral size of such features ranges between several and tens of nanometers with the height of up to 1 nm. It has been suggested that the presence of ripples could be one of the factors ultimately limiting mobility of carriers and that it may be also responsible, by introducing an effective gauge field, for the lack of weak localization observed in certain graphene samples. In the present contribution the transport properties of the rippled graphene are studied theoretically starting with the simple case of one-dimensional modulation. Using either single-band or the full sp^3 tight-binding Hamiltonians we compare and discuss the importance of two ripple-related mechanisms of scattering: the variation of interatomic distances and hybridization between π and σ bands of graphene.
12
Content available remote

Graphene Conductance in the Presence of Resonant Impurities

80%
Inglot M., Dugaev V.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 2
163-165
EN
We discuss transport properties of graphene related to the resonant scattering from impurities and defects. Two different models describing defects in the bulk of graphene or at the graphene surface are used for the calculation of self energy of electrons scattered from short-range impurities or defects. The results of numerical calculations demonstrate a resonant character of resistance. In the case of neutral impurities or defects the scattering also leads to a resonant decrease of the spin relaxation time.
13
Content available remote

Effect of Disorder on Spin and Charge Excitations in the Fractional Quantum Hall Effect

80%
Výborný K., Müller C., Dethlefsen A., Haug R., Wójs A.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
249-254
EN
A simple model of disorder in fractional quantum Hall systems is combined with the standard exact diagonalisation technique. Electron-density-dependent gaps at filling factors 1/3,2/3,2/5, and 3/5 measured by activated transport can then be fitted with a single reasonable value of d which has the meaning of the separation of ionized donors from the quasi-2D electron gas.
14
Content available remote

Correlation Effects and Spin Dependent Transport in Carbon Nanostructures

80%
Lipiński S., Krychowski D.
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vol. 126
|
issue 1
190-193
EN
The impact of symmetry breaking perturbations on the spin dependent transport through carbon nanotube quantum dots in the Kondo regime is discussed. The proposals of spin filter, spin valve and spin battery are presented.
15
Content available remote

Spin and Charge Transport in a Magnetic Tunnel Junction with Magnetic Impurities Embedded in the Tunnel Barrier

80%
Misiorny M., Barnaś J.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 2
196-199
EN
Electronic transport in a nanoscopic magnetic tunnel junction with magnetic particles or magnetic impurity atoms/molecules embedded in the barrier is studied theoretically. The impurity Hamiltonian includes magnetic anisotropy of easy axis type with additional perpendicular term. The description takes into account both elastic tunneling processes as well as inelastic processes associated with a flip of electron spin.
16
Content available remote

Signatures of Transverse Magnetic Anisotropy in Transport through a Large-Spin Molecule in the Kondo Regime

80%
Misiorny M., Weymann I., Barnaś J.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 2
200-203
EN
The effect of transverse magnetic anisotropy on spin-dependent transport through a large-spin molecule strongly tunnel-coupled to ferromagnetic electrodes is analyzed theoretically. In particular, we investigate whether it is possible to observe in transport signatures of oscillations of the ground-state doublet splitting due to the application of an external magnetic field along the molecule's hard axis. We show that magnetic field leads to revivals of the Kondo effect, with the Kondo temperature depending on the magnetic configuration of the device.
17
Content available remote

HgSe Based Mixed Crystals Doped with Fe Resonant Donors

80%
Dobrowolski W.
Acta Physica Polonica A
|
1996
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vol. 89
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issue 1
3-36
EN
The article reviews the physical properties of semimagnetic semiconductors of the type Hg_{1-x-y}Fe_{x}A^{II}_{y}Se_{1-z}B^{VI}_{z} and Hg_{1-x-y}Fe_{x}Mn_{y}Se. Optical, magnetooptical, transport and magnetotransport experiments showed that in Hg_{1-x}Fe_{x}Se substitutional iron forms a resonant donor state whose energy is superimposed on the conduction band continuum. Resulting anomalous properties of electron scattering rate, i.e. strong enhancement of electron mobility (or drop of Dingle temperature), which occur in Hg_{1-x}Fe_{x}Se at low temperatures in a certain Fe concentration range, are described. Next, theoretical models describing this anomalous reduction of the scattering rate are discussed. The description of thermomagnetic, optical, magnetooptical and magnetic properties of Hg_{1-x}Fe_{x}Se, with emphasis on features originating from the peculiar iron level position in the band structure of Hg_{1-x}Fe_{x}Se, conclude the first part of the present paper. In the second part the physical properties of the semiconducting alloys Hg_{1-x}Mn_{x}Se:Fe, Hg_{1-v}Cd_{v}Se:Fe, Hg_{1-x}Zn_{x}Se:Fe, HgSe_{1-x}Te_{x}:Fe and HgSe_{1-x}S_{x}:Fe are described. In particular, the dependence of the position of the Fe resonant donor state in the band structure on the crystal composition is discussed. The values of predicted Γ_{6} and Γ_{8} band offsets between HgSe and CdSe, HgTe, MnSe and ZnSe are given. The considerable attention is paid to the discussion of the mechanism limiting the electron mobility in the mixed alloys. Finally, topics which have not been explicitly covered in this review are mentioned and open problems are discussed.
18
Content available remote

Carrier Heating Efficiency in Optically Detected Cyclotron Resonance Experiment

80%
Dedulewicz S., Godlewski M.
Acta Physica Polonica A
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1993
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vol. 84
|
issue 3
535-537
EN
Monte Carlo calculations of carrier heating efficiency in optically detected cyclotron resonance experiment are presented. It is shown that electrons accelerated by microwave electric field gain energy sufficient for impact ionization of shallow centers and for exciton dissociation. It is also explained why very sharp thresholds for impact processes were observed in the optically detected cyclotron resonance investigations.
19
Content available remote

Vertex Corrections to the Electrical Conductivity of the Disordered Falicov-Kimball Model

80%
Pokorný V., Janiš V.
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issue 5
922-923
EN
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.
20
Content available remote

Peculiarities of Electron Transport in PbTe:Cr due to Presence of Resonant Impurity State

80%
Grodzicka E., Dobrowolski W., Kossut J., Story T., Witkowska B.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
599-603
EN
The results of transport investigation of Pb_{1-x}Cr_{x}Te (x ≤ 0.009) in temperature range 3.5-300 K are presented. The obtained electron concentration and electron mobility vs. temperature and Cr concentration data are interpreted and discussed within the model assuming that Cr in PbTe forms a donor state resonant with the conduction band.
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