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Wyświetlanie 1-12 z 12
Tytuł:
Temperature Dependence of the Zero-Bias Conductance in the Graphene NIS Junction
Autorzy:
Wysokiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1374348.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.45.+c
73.23.Ad
Opis:
The temperature dependence of the zero-bias conductance of the graphene-based, ballistic junction composed of the three consecutive regions: normal, with potential barrier ("insulating") and superconducting (NIS), is analyzed within the extended Blonder-Tinkham-Klapwijk approach. Within this approach we have found that oscillatory behavior of the conductance as a function of barrier strength is suppressed by the temperature - the amplitude diminishes with heating up the junction. Moreover, the subtle, although nontrivial feature of the system is reported: the average over the period of the oscillations of the zero-bias conductance for relatively small Fermi level mismatch behaves non-monotonically with the increase of the temperature with the maximum roughly at T/$T_{c}$ ≈ 0.5.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-36-A-39
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exciton Electro-Absorption at Non-Zero Wave Vector
Autorzy:
Slawik, M.
Petelenz, P.
Powiązania:
https://bibliotekanauki.pl/articles/1933598.pdf
Data publikacji:
1995-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Jw
78.20.-e
78.40.-q
Opis:
Based on a previously proposed two-dimensional model of a polyacene crystal, the contributions to the electro-absorption signal from different points of the exciton Brillouin zone are calculated. They are shown to differ substantially both in amplitude and in shape. This makes electro-absorption spectra very sensitive to vibronic coupling. On the one hand, the new factor is a potential complication in theoretical interpretations. On the other hand, it favours electro-absorption spectroscopy as a promising experimental tool to study vibronic effects.
Źródło:
Acta Physica Polonica A; 1995, 88, 2; 401-409
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transition Rate Dependence on the Non-Zero Initial Momentum in the ADK-Theory
Autorzy:
Ristić, V. M.
Miladinović, T. T.
Radulović, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/2047850.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
32.80.-t
32.80.Fb
32.80.Rm
Opis:
Tunneling regime, introduced by Keldysh, in the interaction of strong lasers with atoms has been now accepted as the reliable method for describing processes when low frequency lasers are involved. Yet it was always assumed that the ionized electrons are leaving the atom with zero initial momentum. Because we are interested in how non-zero momentum influences the transition probability of tunnel ionization, we obtained the exact expression for the momentum. Here the estimation of the transition probability with nonzero momentum included was conducted. Potassium atoms in the laser field whose intensity varied from 10$\text{}^{13}$ W/cm$\text{}^{2}$ to 10$\text{}^{14}$ W/cm$\text{}^{2}$ were studied. It seems that all energy of laser field is used for tunneling ionization process at the beginning of laser pulse - ionization probability is large. After that, with further action of laser pulse, ionization probability decreases, probably because part of laser pulse energy is used for increasing momentum of ejected electrons, leaving smaller amounts of light quanta available for ionization of remaining electrons. If laser pulse lasts long enough, then the amounts of light quanta available for ionization become larger, resulting in increase in ionization probability, now with greater starting energy of ejected electrons.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 909-914
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Zero-Index Metamaterial Single Layer Superstrate for Patch Antenna Gain Enhancement
Autorzy:
Saleh, C.
Bensafieddine, D.
Laamari, E.
Bouzouad, M.
Powiązania:
https://bibliotekanauki.pl/articles/1402358.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Pt
84.40.Ba
Opis:
The objective of this paper is to use a zero refractive index n metamaterial as single layer superstrate suspended above a microstrip patch antenna (MPA), operating at 43 GHz, for the gain enhancement. The single metamaterial layer superstrate is composed of a periodic arrangement of Jerusalem cross unit-cells, and behaves as an homogeneous medium characterized by a refractive index close to zero. This metamaterial low index property allows gathering radiated waves from the antenna and collimates them towards the superstrate normal direction. The proposed design improves the antenna gain by 5.1 dB.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-307-B-309
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zero Temperature Magnetic Frustration in Nona-Membered s=3/2 Spin Rings with Bond Defect
Autorzy:
Antkowiak, M.
Kozłowski, P.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1427128.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.10.Jm
Opis:
Zero-temperature limits of the local and global thermodynamic quantities in the nine-membered antiferromagnetic s=3/2 spin ring are investigated by means of numerical exact diagonalization. An anisotropic Heisenberg model with tunable bond defect reflecting continuously varying topology (from closed to open ring) is exploited. The frustrated and non-frustrated phases are identified in the ground-state phase diagram determined by a bond-defect strength and magnetic field. Near the phase boundaries significance of the thermal fluctuations affecting the estimates of the local magnetic quantities found earlier at T=1 K is revealed. For the global quantities the effects of thermal fluctuations are found much weaker. A sequence of the local magnetic moments is analysed and their experimental verification at the edges of the non-frustrated and within the entire frustrated phase is suggested at sufficiently low temperature.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1102-1104
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Hydrostatic Pressure on the Zero-Field Splitting in NiSnCl$\text{}_{6}$·6H$\text{}_{2}$O
Autorzy:
Krupska, A.
Krupski, M.
Powiązania:
https://bibliotekanauki.pl/articles/2035745.pdf
Data publikacji:
2003-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.50.+p
76.30.Fc
Opis:
The dependence of the crystal-field splitting parameter D in NiSnCl$\text{}_{6}$·6H$\text{}_{2}$O on hydrostatic pressure was determined by the electron paramagnetic resonance method, for the pressures up to 500 MPa. The derivative (∂D/∂p)$\text{}_{T}$ as well as the temperatures and pressures at which the D-parameter reaches zero, were determined. The molecular mechanism responsible for the temperature and pressure changes of the D-parameter is similar to that one observed in the isomorphic NiSiF$\text{}_{6}$·6H$\text{}_{2}$O.
Źródło:
Acta Physica Polonica A; 2003, 103, 5; 453-458
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zero Field Spin Splitting in GaN/AlGaN Heterostructures Probed by the Weak Antilocalization
Autorzy:
Dybko, K.
Siekacz, M.
Skierbiszewski, C.
Powiązania:
https://bibliotekanauki.pl/articles/1811927.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ej
73.43.Qt
73.20.Fz
Opis:
We present the magnetoconductivity measurements of a high mobility two-dimensional electron gas confined at GaN/AlGaN interface. The sensitive measurements of low field conductivity revealed both quantum corrections, the weak localization and antilocalization effects. It indicates the importance of the spin-orbit coupling in this wide band gap material. The analysis of the data provided the information about the temperature dependence of the dephasing time and total spin-orbit relaxation time. The conduction band spin splitting energy amounts to 0.23 meV and 0.35 meV at electron densities $2.2×10^{12} cm^{-2}$ and $5.7×10^{12} cm^{-2}, respectively.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1109-1113
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculating Ionization Transition Rate for Circularly Polarized Fields, Including Non-Zero Initial Momentum
Autorzy:
Ristić, V.
Miladinović, T.
Radulović, M.
Powiązania:
https://bibliotekanauki.pl/articles/1791204.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
32.80.-t
32.80.Fb
32.80.Rm
Opis:
Potassium atoms in circularly polarized laser field whose intensity (I) varies from 2× $10^{12}$ W/$cm^2$ to 2.5× $10^{14}$ W/$cm^2$ were studied. In the case when there is zero initial momentum, transition rate (that depends only on I) exhibits standard behaviour: as I increases, so thus the rate, until it reaches its maximum value at 1.1× $10^{14}$ W/$cm^2$; after that, rate diminishes as I increases. In the case of non-zero initial momentum, transition rate (that now depends on I but additionally on initial momentum, too) exhibits following behaviour: dependence of the rate on I follows standard pattern, it rises with increase of I until it reaches its maximum, and then diminishes. But with increase of momentum, ionization rate gradually diminishes.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 504-506
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Exact Solution of the Mixed-Spin Ising Chain with Axial and Rhombic Zero-Field Splitting Parameters
Autorzy:
Dančo, M.
Strečka, J.
Powiązania:
https://bibliotekanauki.pl/articles/1506905.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
05.70.Jk
75.10.Pq
Opis:
Ground-state phase diagram of the mixed spin-1/2 and spin-1 Ising chain with axial and rhombic zero-field splitting parameters is exactly calculated within the framework of the transfer-matrix method. It is shown that the rhombic zero-field splitting parameter prefers the magnetically ordered phase instead of the disordered phase.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 728-729
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Implications of Invalid Conversions between Crystal-Field Parameters and Zero-Field Splitting Ones Used in Superposition Model
Autorzy:
Rudowicz, C.
Karbowiak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1365340.pdf
Data publikacji:
2014-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
76.30.Fc
71.70.Ch
75.10.Dg
Opis:
The methodology used in recent study of the zero-field splitting parameters of $Cr^{3+}$ ions at various orthorhombic symmetry sites in $LiKSO_4$ by Pandey and Kripal is critically commented on. We argue that the crystal field parameters, $B_{kq}$, in the Wybourne notation, which were calculated using the superposition model for $Cr^{3+}$ ions in $LiKSO_4$, may only be converted into the crystal field parameters in the Stevens notation. Regrettably, the authors have also converted the latter parameters supposedly into the zero-field splitting parameters D and E in the conventional notation. Such direct conversions are fundamentally incorrect and constitute factual invalid usage of the conversion relations between the crystal field (ligand field) parameters and the zero-field splitting ones. The cases of an implied usage of the invalid conversion relations between the crystal field parameters and the zero-field splitting parameters occurring in recent literature are also outlined. Pandey and Kripal have found the zero-field splitting parameters theoretically evaluated in this way to be in good agreement with the experimental values. However, the faulty methodology renders the conclusion that $Cr^{3+}$ ions enter into the $LiKSO_4$ lattice at the substitutional $K^{+}$ sites unjustified. Several other conceptual problems arising from misinterpretations of the crucial notions identified therein are also discussed and clarified.
Źródło:
Acta Physica Polonica A; 2014, 125, 5; 1215-1219
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conversions of the Second-Rank Zero Field Splitting Parameters Measured Assuming the Fictitious Spin S=1 to those for the Effective Spin S̃=2
Autorzy:
Kozanecki, M.
Rudowicz, C.
Powiązania:
https://bibliotekanauki.pl/articles/1030215.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
75.10.Dg
76.30.-v
76.30.Fc
Opis:
We investigate feasibility of comparison between the zero field splitting parameters obtained experimentally based on the spin Hamiltonian with the fictitious spin S'=1 and those with the effective spin S̃=2. The former zero field splitting parameters have recently been measured for Fe²⁺ ions in forsterite Mg₂SiO₄, whereas the latter zero field splitting parameters are available in literature, e.g. for Fe²⁺ and Cr²⁺ (S̃=2) ions. It turns out that no unique direct comparison is feasible and hence appropriate conversion relations need to be derived. Methodology for such conversions is outlined. Various combinations of the possible energy level schemes for the spin S̃=2 and S'=1 are briefly described. Illustrative preliminary results concerning appropriate conversions of the second-rank zero field splitting parameters measured by high-frequency EMR for Fe²⁺ in natural and synthetic forsterite are presented. Detailed results and full analysis will be given elsewhere.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 11-14
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative analysis of experimental and theoretical zero-field splitting and Zeeman electronic parameters for Fe²⁺ ions in FeX₂·4H₂O (X = F, Cl, Br, I) and [Fe(H₂O)₆](NH₄)₂(SO₄)₂
Autorzy:
Zając, M.
Rudowicz, C.
Powiązania:
https://bibliotekanauki.pl/articles/1055040.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.35.+r
71.70.Ch
71.70.Ej
76.20.+q
76.30.-v
76.30.Fc
87.80.Lg
Opis:
Spectroscopic and magnetic properties of Fe²⁺ (3d⁶; S=2) ions at orthorhombic sites in FeX₂·4H₂O (X = F, Cl, Br, I) crystals are compared with those in [Fe(H₂O)₆](NH₄)₂(SO₄)₂ (FASH). The microscopic spin Hamiltonian modeling utilizing the package MSH/VBA enables prediction of the zero-field splitting parameters and the Zeeman electronic ones. Wide ranges of values of the microscopic parameters, i.e. the spin-orbit (λ), spin-spin (ρ) coupling constants, and the crystal-field (ligand-field) energy levels (Δp_{i}) within the ⁵D multiplet are considered to establish the dependence of the zero-field splitting parameters b_{k}^{q} (in the Stevens notation) and the Zeeman factors g_{i} on λ, ρ, and Δp_{i}. By matching the theoretical spin Hamiltonian parameters and the experimental ones measured by EMR, the suitable values of λ, ρ, and Δp_{i} are determined. The novel aspect is prediction of the fourth-rank zero-field splitting parameters and the ρ (spin-spin)-related contributions, not considered in previous studies. The MSH predictions provide guidance for high-magnetic field and high-frequency EMR measurements.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 19-23
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-12 z 12

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