Temat: 74.25.Jb - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Indirect RKKY-Type Interaction by Direct Oxygen Hopping
Autorzy:: Rodriguez-Nuńez, J.
Coqblin, B.
Beck, H.
Konior, J.
Tematy:: 74.20.Mn
74.25.Jb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1930566.pdf Link otwiera się w nowym oknie
Opis:: The three-band Emery model, describing the holes in the CuO$\text{}_{2}$ planes of the high-temperature superconducting oxides, is considered. The model includes the direct oxygen-oxygen hopping integral t$\text{}_{pp}$. The exact Bogolyubov transformation is used to exclude one oxygen band and obtain a two-dimensional Anderson model. Afterward, the effective Hamiltonian is obtained by eliminating the second oxygen band with the use of two approximate canonical transformations. The effective Hamiltonian describes the spins residing on the copper sites and interacting through an indirect interaction J$\text{}_{SX}$(R), where R is the distance between two copper ions. J$\text{}_{SX}$(R) depends on the doping rate δ and is a decaying function of R. Numerical results for J$\text{}_{SX}$(R) are given for different doping rates δ for the case of parabolic bands. The obtained interaction J$\text{}_{SX}$(R), when added to the original antiferromagnetic interaction (present in oxides at δ = 0), might lead to a frustration of the long-range antiferromagnetic ordering upon doping.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Electronic Properties of CeNiAl₄ Based on ab initio Calculations and XPS Measurements
Autorzy:: Werwiński, M.
Chełkowska, G.
Szajek, A.
Kowalczyk, A.
Tematy:: 71.20.b
74.25.Jb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1030430.pdf Link otwiera się w nowym oknie
Opis:: The CeNiAl₄ compound crystallizes in an orthorhombic YNiAl₄-type structure with a Cmcm space group. The earlier susceptibility data and X-ray photoelectron spectroscopy (XPS) suggested a localized character of the 4f states in CeNiAl₄ with a valence state close to a Ce⁺³ ion. In this work we present a combined theoretical and experimental study of the electronic structure for the Kondo dense system CeNiAl₄ based on the XPS data and ab initio calculations. Using the band structure calculations the theoretical XPS valence band spectra are evaluated. Below the Fermi energy the total density of states contains mainly 3d states of Ni hybridized with Ce 4f states.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Calculation of Optical and Spin-Hamiltonian Parameters for $Mn^{4+}$ Doped in $LiGa_{5}O_{8}$
Autorzy:: Ciresan, M.
Stanciu, M.
Avram, N.
Tematy:: 74.25.Jb
74.25.nd
76.30.-v; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1791234.pdf Link otwiera się w nowym oknie
Opis:: The aim of this paper is to investigate, from theoretical point of view, the optical spectra and EPR (g-factors) parameters for $Mn^{4+}:LiGa_{5}O_{8}$. The optical energy levels scheme has been obtained by the diagonalization of the Hamiltonian of the system, using all 50 wave functions of the LS terms of $3d^{3}$ electron configuration. The crystal field parameters have been obtained in the exchange charge model of crystal field, taking into account the structure of the host matrix and effects of the covalent bond formation between the $Mn^{4+}$ with $O^{2-}$. The satisfactory agreement with experimental data is obtained.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Bismuth Valence in a $Tl_{0.7}Bi_{0.3}Sr_{1.6}Ba_{0.4}CaCu_{2}O_{y}$ Superconductor from X-Ray Photoemission Spectroscopy
Autorzy:: Zalecki, R.
Woch, W.
Kowalik, M.
Kołodziejczyk, A.
Gritzner, G.
Tematy:: 74.72.-h
74.25.Jb
79.60.-i; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1537186.pdf Link otwiera się w nowym oknie
Opis:: The X-ray electron photoemission spectra of a $Tl_{0.7}Bi_{0.3}Sr_{1.6}Ba_{0.4}CaCu_2O_{y}$ superconductor were measured with $Al K_{α}$ and $Mg K_{α}$ radiation at room temperature. The Bi 4f spectrum was compared to the same spectra of $Bi_{1.75}Pb_{0.35}Sr_{1.9}Ca_{2.05}Cu_{3.05}O_{y}$ and $Tl_{0.6}Pb_{0.4}Sr_{1.6}Ba_{0.4}Ca_2Cu_3O_{y}$ superconductors. In Bi,Pb-based superconductor only one type of $Bi^{3+}$ ions is present. The Bi 4f spectrum in the Tl,Bi-superconductor consists of two contributions due to the different valences. The component from $Bi^{5+}$ lines is in higher binding energy than from $Bi^{3+}$. The ratio of trivalent $Bi^{3+}$ to pentavalent $Bi^{5+}$ bismuth ions was calculated from decomposition of the spin-orbit split spectrum of the Bi 4f photoelectrons. The conclusion is that Bi is present in trivalent and in pentavalent form and the ratio of $Bi^{3+}$ to $Bi^{5+}$ is 1.87 ± 0.02.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Cooper Pair in Two Nonstandard Situations
Autorzy:: Wróbel, P.
Starypan, Z.
Kaczmarczyk, J.
Spałek, J.
Tematy:: 74.20.-z
74.25.Jb
71.10.-w; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2046740.pdf Link otwiera się w nowym oknie
Opis:: We summarize briefly our recent work on the bound states of two electrons (Cooper pairs) in two nonstandard situations: when the quasiparticle masses depend on spin and when an electron pair is localized on a two-dimensional quantum dot and placed in an applied magnetic field. In both cases we are dealing with an extension of the original Cooper approach. The applicability of the results is briefly mentioned.
Dostawca treści:: Biblioteka Nauki

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na półce

Skocz do pozycji: 6.

Tytuł:: Improved Transresistance Characteristics of Inductance-gate Type SFFT Using AFM Lithography
Autorzy:: Ko, S.
Tematy:: 74.20.Pq
74.25.F-
74.25.Jb
74.55.+V; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1400571.pdf Link otwiera się w nowym oknie
Opis:: An atomic force microscope (AFM) was used to locally anodize the serial channels of an inductance-gate type superconducting flux flow transistor (SFFT) as narrow slits with a width of 50 μm, a space of 25 μm, and 12 turns, to improve the transresistance value. Among the serial channels that were anodized with the scanning tip of the AFM in the drain current line, channels 1 and 2 were 7.3 and 7.9 μm wide, and 531 and 461 nm high, respectively. The critical current density in the serial channel of the fabricated SFFT, which was determined using an AFM modification method, was decreased by increasing the gate current. The measured current-voltage curves were compared with the simulated ones. The maximum transresistance value was 0.56 Ω at the drain current of 20 mA when the gate current was 6 mA. The transresistance characteristics of the inductance-gate type SFFT could be more improved than that of the single-channel type SFFT using an inductively coupled plasma lithography method
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Simple Band Model of Doped Fullerene Crystal
Autorzy:: Koper, A.
Mucha, M.
Tematy:: 74.20.Mn
74.25.Kc
74.25.Jb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2012907.pdf Link otwiera się w nowym oknie
Opis:: We use quantum billiard with many scattering centers to describe conducting electrons properties in A$\text{}_{n}$C$\text{}_{60}$ crystals, where A denotes alkali metal. We focus our attention on the A$\text{}_{3}$C$\text{}_{60}$ crystal, for which we calculate the band structure, density of states, and conductivity for normal electrons. Conductivity shows linear dependence on temperature in this model, which agrees well with experimental data. We also discuss consequences of our results for superconductivity mechanism in A$\text{}_{3}$C$\text{}_{60}$ and possibilities of analogous approach to describe electron properties in fused fullerenes and multiply connected carbon clusters.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: The Pseudogap Phenomenon in High-T$\text{}_{c}$ Superconductors
Autorzy:: Ranninger, J.
Romano, A.
Tematy:: 74.20.-z
74.25.-q
74.25.Jb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2011238.pdf Link otwiera się w nowym oknie
Opis:: We review the possible mechanisms leading up to the phenomenon of a pseudogap which characterizes the normal-state properties of high-T$\text{}_{c}$ superconductors. We suggest that this pseudogap is not due to superconducting phase fluctuations and hence is not related to a crossover between a BCS state of Cooper pairs and a Bose-Einstein condensation of local pairs. We rather argue that it is due to uncorrelated pairing which is already manifest in the local electronic structure and accessible by photoemission and tunneling experiments.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Superconductivity, Weak Itinerant Ferromagnetism and Electronic Band Structure of Y$\text{}_{9}$Co$\text{}_{7}$
Autorzy:: Kołodziejczyk, A.
Wiendlocha, B.
Zalecki, R.
Toboła, J.
Kaprzyk, S.
Tematy:: 74.25.Jb
74.25.Ha
74.20.Mn; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2047310.pdf Link otwiera się w nowym oknie
Opis:: The paper presents experimental results for the intermetallic compound Y$\text{}_{9}$Co$\text{}_{7}$ which is the first very weak itinerant ferromagnetic superconductor. The measurements of electrical resistivity, susceptibility, magnetization, specific heat, nuclear magnetic resonance, and other properties show the magnetic transition at T$\text{}_{C}$≈ 4.5 K and the onset of superconductivity at about T$\text{}_{S}$≈ 2.5 K, revealing the coexistence state within a temperature interval below T$\text{}_{S}$. A few of the results are shortly reviewed and discussed. We focus attention on our recent ultraviolet photoemission spectroscopy and their comparison with our band structure calculations. Interpretations are considered which take into account the characteristic structure of the compound and different possible types of magnetic ordering.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Mixed Valence Quasiparticles in CuO$\text{}_{2}$ Planes
Autorzy:: Bała, J.
Oleś, A. M.
Tematy:: 74.25.Jb
75.30.Ds
75.10.Lp; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1955491.pdf Link otwiera się w nowym oknie
Opis:: The motion of a single hole doped to a CuO$\text{}_{2}$ plane of a high temperature superconductor is described by a spin-fermion model which treats explicitly the hybridization with the upper Hubbard band. One finds that sectors of Zhang-Rice bound states coexist with reasonably damped oxygen and copper-like quasiparticles, with a considerable transfer of the spectral weight to the upper Hubbard band. The oxygen states have small dispersions and can be identified in the angle-resolved photoemission experiments for Bi$\text{}_{2}$Sr$\text{}_{2}$CaCu$\text{}_{2}$O$\text{}_{8}$.
Dostawca treści:: Biblioteka Nauki

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