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    Wyświetlanie 1-11 z 11
    Tytuł:
    Electromagnetic Response in Kinetic Energy Driven Superconductivity: the Meissner Effect
    Autorzy:
    Krzyzosiak, M.
    Lan, Y.
    Feng, S.
    Jacak, L.
    Gonczarek, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1536649.pdf
    Data publikacji:
    2010-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.25.Ha
    74.25.N-
    74.20.Mn
    Opis:
    Electromagnetic response of cuprate superconductors is studied within the model of kinetic energy driven d-wave superconductivity by analyzing the Meissner effect. The kernel of the linear response function is found and employed to calculate the magnetic field penetration depth and the superfluid density of cuprate superconductors within the specular reflection model for a purely transverse vector potential. It is shown that the magnetic field penetration depth and the superfluid density depend linearly on temperature, except for a strong deviation from the linear characteristics at extremely low temperatures, which is attributed to nonlocal effects. The zero-temperature superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance in the theoretical description of the electromagnetic response is addressed, and an approximation which does not violate local charge conservation is proposed.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 2; 283-288
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spinning Superconductors and Ferromagnets
    Autorzy:
    Hirsch, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1029748.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.20.-z
    74.25.N-
    75.70.Tj
    Opis:
    When a magnetic field is applied to a ferromagnetic body it starts to spin (Einstein-de Haas effect). This demonstrates the intimate connection between the electron's magnetic moment μ_{B}=eħ/2m_{e}c, associated with its spin angular momentum S=ħ/2, and ferromagnetism. When a magnetic field is applied to a superconducting body it also starts to spin (gyromagnetic effect), and when a normal metal in a magnetic field becomes superconducting and expels the magnetic field (Meissner effect) the body also starts to spin. Yet according to the conventional theory of superconductivity the electron's spin only role is to label states, and the electron's magnetic moment plays no role in superconductivity. Instead, within the unconventional theory of hole superconductivity, the electron's spin and associated magnetic moment play a fundamental role in superconductivity. Just like in ferromagnets the magnetization of superconductors is predicted to result from an aggregation of magnetic moments with angular momenta ħ/2. This gives rise to a "Spin Meissner effect", the existence of a spin current in the ground state of superconductors. The theory explains how a superconducting body starts spinning when it expels magnetic fields, which we argue is not explained by the conventional theory, it provides a dynamical explanation for the Meissner effect, which we argue the conventional theory cannot do, and it explains how supercurrents stop without dissipation, which we argue the conventional theory fails to explain. Essential elements of the theory of hole superconductivity are that superconductivity is driven by lowering of kinetic energy, which we have also proposed is true for ferromagnets], that the normal state charge carriers in superconducting materials are holes, and that the spin-orbit interaction plays a key role in superconductivity. The theory is proposed to apply to all superconductors.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 350-355
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Magnetic History on AC Loss Minimum in BSCCO-2223 Composite Tape
    Autorzy:
    Maievskyi, E.
    Ciszek, M.
    Trojanowski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398595.pdf
    Data publikacji:
    2016-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    84.71.Mn
    74.25.N-
    74.25.Sv
    74.25.Wx
    Opis:
    In the paper we report experimental results of AC magnetization losses in a multi-filamentary BSCCO-2223 superconducting composite tape due to coaxial AC and DC magnetic fields subjected perpendicularly to the plane of the tape. Such superposition of magnetic fields usually leads to some reduction of magnetization losses. A distinguished minimum in the AC loss is observed, at a certain DC bias magnetic field and at a certain fixed magnetic field amplitude. It is shown that the minimum of the AC losses very strongly depends on magnetic history of the investigated tape, which is directly related to the magnetic flux trapping within tape's superconducting filaments region. Measurements were carried out with a sinusoidally varying magnetic fields at amplitudes up to 100 mT and a superimposed DC magnetic field up to 50 mT, at frequency range of 21-113 Hz.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 2; 527-530
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Quantization of electromagnetic modes in a hyperbolic negative-index layered superconductor slab
    Autorzy:
    Cortés-López, S.
    Pérez-Rodríguez, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/1062050.pdf
    Data publikacji:
    2016-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.25.Gz
    74.25.N-
    74.78.Fk
    78.67.Pt
    Opis:
    We theoretically study the infrared reflectivity and transmissivity of a high-temperature layered superconductor slab. Both infrared spectra exhibit very narrow Fabry-Perot resonances associated with the quantization of the wave vector of the TM electromagnetic modes. The resonances are observed in a pass band where the refractive index of the layered superconductor is negative. The pass band of negative dispersion is above the Josephson plasma frequency which appears in the expression for the effective permittivity component, corresponding to the direction perpendicular to the layers. It was found that the Fabry-Perot resonances undergo a blue shift as the slab thickness or the angle of incidence are increased. Moreover, the quantized electromagnetic modes turn out to be quasi-longitudinal because of the strong anisotropy of the infrared dielectric response of the layered superconductor.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 2; 641-644
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Obtaining a Rough Flux Front in Type-II Superconductors Using a Critical State Model
    Autorzy:
    Romero-Salazar, C.
    Hernández-Flores, O.
    Chabanenko, V.
    Kuchuk, E.
    Abaloszewa, I.
    Nabialek, A.
    Pérez-Rodríguez, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398648.pdf
    Data publikacji:
    2016-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.20.-z
    74.20.De
    74.25.Ha
    74.25.N-
    74.25.Op
    74.25.Sv
    74.25.Wx
    74.62.Dh
    74.81.-g
    Opis:
    In this work we numerically modelled a periodic magnetic flux pattern which qualitatively reproduces the so-called sand avalanches scenario in type-II superconductors. To model these sand-pile patterns we consider a perturbation on the critical current which, as a first approximation, follows a periodic function which depends on the position.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 2; 645-648
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phase Diagram and Activation Energy for Vortex Pinning in Nb/(Co,Pd) Superconductor-Ferromagnet Bilayer
    Autorzy:
    Syryanyy, Y.
    Aleszkiewicz, M.
    Cieplak, Marta
    Zhu, L.
    Chien, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/1374109.pdf
    Data publikacji:
    2014-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.25.F-
    74.25.N-
    74.25.Wx
    74.62.-c
    74.70.-b
    74.78.-w
    74.78.Fk
    75.70.Kw
    75.70.-i
    Opis:
    Using the magnetoresistance measurements we study the phase transition line and the activation energy for vortex pinning in superconductor/ferromagnet bilayer, built of a ferromagnetic Co/Pd multilayer with perpendicular magnetic anisotropy, and a niobium film, with insulating layer in-between to eliminate proximity effect. The domain width is reversibly pre-defined using the angle-dependent demagnetization. We find that the enhancement of the activation energy for vortex pinning by magnetic domains is rather modest, by a factor of about 2.1. We attribute this to large domain width, and large dispersion of the domain width in this bilayer.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 4a; A-123-A-126
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermal Fluctuations of $(Tl_{0.5}Pb_{0.5})Sr_2(Ca_{0.9}Gd_{0.1})Cu_2O_{z}$ Bulk Superconductor
    Autorzy:
    Woch, W.
    Chrobak, M.
    Kołodziejczyk, A.
    Gritzner, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1426876.pdf
    Data publikacji:
    2012-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.72.-h
    74.40.-n
    74.20.De
    74.25.Ha
    Opis:
    We report on the critical fluctuations from the magnetoresistance measurements in polycrystalline $(Tl_{0.5}Pb_{0.5})Sr_2(Ca_{0.9}Gd_{0.1})Cu_2O_{z}$ superconductor. The critical exponents have been calculated above the critical temperature $T_{c}$ as well as in the temperatures interval close to the zero resistance critical temperature. Above $T_{c}$ only Gaussian fluctuations have been observed in a three-dimensional fluctuating system. Additionally, far above $T_{c}$ the applied magnetic field induces the crossover from 3D to 2D fluctuating system. At the temperatures range close to the zero critical temperature the properties of the weak links are dominating and the fluctuating phase in each grain becomes long-range ordered as a consequence of the activation of weak links between grains.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 5-6; 1059-1062
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of Resistive Superconducting Transition of Thallium Based Superconductors
    Autorzy:
    Woch, W.
    Zalecki, R.
    Chrobak, M.
    Kołodziejczyk, A.
    Gritzner, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1431253.pdf
    Data publikacji:
    2012-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.72.-h
    74.40.n
    74.20.De
    74.25.Ha
    Opis:
    A width and shape of resistive transition as well as thermal fluctuations of the thallium based superconductors were analyzed theoretically. The applied magnetic field widens the resistive transition according to the following formula: $ΔT=CH^{m}+ΔT_{0}$. The exponent m fluctuates around 2/3 and depends on vortex structure and strength of the pinning force. The shape of the resistive transition was fitted by two models: the first one based on Ambegaokar-Halperin theory and the other one based on Anderson-Kim theory expressed by the exponential formula. Critical fluctuations were analyzed on the basis of magnetoresistance measurements results. The critical exponents have been calculated above the critical temperature $T_{c}$ as well as for temperatures close to the zero resistance critical temperature.
    Źródło:
    Acta Physica Polonica A; 2012, 121, 4; 789-795
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fault Current Limitation by 2G HTS Superconducting Transformer - Experimental Investigation
    Autorzy:
    Wojtasiewicz, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398591.pdf
    Data publikacji:
    2016-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.90.+n
    84.70.+p
    84.71.-b
    85.25.-j
    85.25.Am
    85.25.Qc
    Opis:
    Transformers represent one of the oldest and most mature elements in a power transmission and distribution network. The new superconducting transformers are smaller and lighter than conventional ones and they have lower power losses, too. Also, the new 2G superconducting tapes with high resistivity in the normal state allow to build transformers with high short-circuit strength. The short-circuit current limiting feature of the superconducting transformer, which is the most important benefit of replacing conventional windings by superconducting ones, provides protection and significantly reduces the wear and tear of circuit breakers and other substation power equipment. This paper describes the design and experimental investigations results of a model of a 1-phase, 8.8 kVA superconducting transformer with windings made of 2G HTS tape. A special regard is given to the ability of the device's superconducting winding to limit the short-circuit current, in particular its equivalent resistance in normal state at a temperature of 77 K (i.e. resistance of the resistive layers of the HTS tape just after transition to the non-superconducting state).
    Źródło:
    Acta Physica Polonica A; 2016, 130, 2; 516-520
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electro-Optical Properties of II-VI Superlattices
    Autorzy:
    Schillak, P.
    Czajkowski, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/2047684.pdf
    Data publikacji:
    2007-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.35.Cc
    73.21.Cd
    74.25.Gz
    78.20.Jq
    78.67.-n
    Opis:
    We show how to compute electro-optical spectra of semiconductor superlattices in the region of interband electronic transitions. The method uses the microscopic calculation of eigenvalues and eigenfunctions and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities. The electron-hole screened Coulomb potential is adapted and the valence band structure is taken into account in the cylindrical approximation, thus separating light- and heavy-hole motions. We calculate the electro-optical functions, including the optical Stokes parameters and ellipsometric functions for the case of oblique incidence. Results are given for Zn$\text{}_{1-x}$Cd$\text{}_{x}$Se/ZnSe superlattices and a good agreement with experiments is obtained.
    Źródło:
    Acta Physica Polonica A; 2007, 112, 2; 301-304
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Superconducting Devices for Power Engineering
    Autorzy:
    Janowski, T.
    Kondratowicz-Kucewicz, B.
    Wojtasiewicz, G.
    Kozak, S.
    Kozak, J.
    Majka, M.
    Jaroszyński, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1398596.pdf
    Data publikacji:
    2016-08
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.90.+n
    84.60.Ve
    84.70.+p
    84.71.-b
    84.71.Ba
    84.71.Mn
    85.25.-j
    85.25.Am
    85.25.Qc
    Opis:
    The paper presents the current state of research on superconducting devices for the electrical power system, i.e. transformers, fault-current limiters, and energy storages. In particular, it describes scientific achievements of the Laboratory of Superconducting Technologies of Electrotechnical Institute. The development of distributed and renewable energy sources, as well as the increasing number of receivers with low power factor will rise interest in superconducting fault-current limiters and superconducting transformers rated below 1 MVA. Previous studies were focused on the largest power transformers and highest current superconducting fault-current limiters. ReBCO coated conductors allow to build efficient superconducting AC devices. Superconducting tape of a layered structure (second generation HTS tape) enables the construction of transformer rated up to a few MVA without the usage of parallel conductors. Relatively high resistance of the tape in normal state allows to build fault-current limiters and fault-current limiting transformers. Superconducting transformers and superconducting fault-current limiters can help to increase connected power of distribution stations and thereby accelerate development of renewable energy sources.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 2; 537-544
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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