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Wyświetlanie 1-5 z 5
Tytuł:
Electronic Structure and Transport in Approximants of the Penrose Tiling
Autorzy:
Trambly de Laissardière, G.
Szállás, A.
Mayou, D.
Powiązania:
https://bibliotekanauki.pl/articles/1373694.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.Ft
71.30.+h
72.15.Rn
71.23.An
Opis:
We present numerical calculations of electronic structure and transport in the Penrose approximants. The electronic structure of perfect approximants shows a spiky density of states and a tendency to localization that is more pronounced in the middle of the band. Near the band edges the behavior is more similar to that of free electrons. These calculations of band structure and in particular the band scaling suggest an anomalous quantum diffusion when compared to normal ballistic crystals. This is confirmed by a numerical calculation of quantum diffusion which shows a crossover from normal ballistic propagation at long times to anomalous, possibly insulator-like, behavior at short times. The time scale $t^*(E)$ for this crossover is computed for several approximants and is detailed. The consequences for electronic conductivity are discussed in the context of the relaxation time approximation. The metallic-like or non-metallic-like behavior of the conductivity is dictated by the comparison between the scattering time due to defects and the time scale $t^*(E)$.
Źródło:
Acta Physica Polonica A; 2014, 126, 2; 617-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoemission and Optical Spectroscopy of i-ZnMgEr Quasicrystal
Autorzy:
Suchodolskis, A.
Assmus, W.
Babonas, G.-J.
Giovanelli, L.
Karlsson, U. O.
Karpus, V.
Le Lay, G.
Rėza, A.
Uhrig, E.
Powiązania:
https://bibliotekanauki.pl/articles/2041813.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.Ft
Opis:
The results of photoemission and optical studies of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10$\text{}^{-10}$ mbar pressure and low, 140-150 K temperature. The valence band photoemission spectra measured reveal a simple metal-type valence band of icosahedral ZnMgEr with a distinct Fermi edge cut-off and with a sharp pseudogap feature. The photoemission spectra of shallow Mg 2p and Zn 3d core levels indicate a coordination shift of Mg 2p spin-orbit doublet and an oscillating dependence of Zn 3d photoemission line components on the photon energy within the hν=20-160 eV range investigated. The optical response of icosahedral ZnMgEr, a dispersion of the dielectric function, was measured by the spectroscopic ellipsometry technique in the 0.5-5.0 eV spectral range. The optical spectra of the quasicrystal indicate the Drude-type optical response superimposed with a peak of interband optical transitions. The interband optical transitions can be modelled with the pseudogap parameters which agree with those deduced in an analysis of the photoemission valence band spectra.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 412-419
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Response of fci-ZnMgHo Quasicrystal
Autorzy:
Karpus, V.
Babonas, G.
Rėza, A.
Suchodolskis, A.
Tumėnas, S.
Hunderi, O.
Assmus, W.
Brűhne, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813393.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.Ft
Opis:
The results of an optical spectroscopy study of the icosahedral fci-ZnMgHo quasicrystal are presented. The dielectric function of the quasicrystal was measured by the spectroscopic ellipsometry technique in the spectral range of 0.1-5.0 eV. The analysis of the dielectric function shows that an optical response of fci-ZnMgHo is a superposition of the free-electron Drude-type contribution and that of the interband transitions across the fci-ZnMgHo pseudogap.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 1005-1008
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Curie Temperature and Density of States at the Fermi Level for Al-Cu-Fe Phases: β-Solid State Solution-Approximants-Icosahedral Quasicrystals
Autorzy:
Shalaeva, E.
Prekul, A.
Shchegolikhina, N.
Medvedeva, N.
Powiązania:
https://bibliotekanauki.pl/articles/1373475.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.-g
71.23.Ft
71.20.-b
61.66.Dk
Opis:
A consistent reduction in the absolute value of the negative paramagnetic Curie temperature was found in a series of Al-Cu-Fe phases: β(CsCl)-solid state solution, noncanonical approximant (η-AlCu(Fe) phase), rational approximants (P1+P2-pentagonal phases) and icosahedral quasicrystal. For these Al-Cu-Fe phases, the decrease in the Curie temperature correlates with a reduction of the density of states at the Fermi level which was estimated from the low-temperature heat capacity measurements and first-principles calculations. The observed correlation was related to the antiferromagnetic indirect exchange interaction (Ruderman-Kittel-Kasuya-Yosida interaction) between the localized magnetic moments on Fe induced by the intrinsic structural defects in the Al-Cu-Fe phases. The weakening of Fe 3d-Al s, p hybridization owing to the intrinsic structural defects such as vacancies, antisite defects and distortions of coordination polyhedrons is suggested to be the main mechanism of appearance of localized magnetic moments on Fe atoms.
Źródło:
Acta Physica Polonica A; 2014, 126, 2; 572-576
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fermi Surface-Brillouin Zone Interactions in 2/1-2/1-2/1 Bergman-Type Approximant $Na_{27}Au_{27}Ga_{31}$
Autorzy:
Mizutani, U.
Sato, H.
Inukai, M.
Zijlstra, E.
Lin, Q.
Corbett, J.
Miller, G.
Powiązania:
https://bibliotekanauki.pl/articles/1373341.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.Ft
71.20.Dg
71.15.Mb
Opis:
The X-ray diffraction studies on a newly synthesized $Na_{26}Au_{25}Ga_{29}$ single crystal revealed the formation of a single phase 2/1-2/1-2/1 Bergman-type approximant and the presence of Au/Ga mixed occupancies in its unit cell containing 680 atoms. The structure model of the 2/1-2/1-2/1 approximant with composition $Na_{27}Au_{27}Ga_{31}$ was constructed by eliminating the chemical disorder with a minimum sacrifice of composition displacement. The full potential linearized augmented plane wave electronic structure calculations with subsequent full potential linearized augmented plane wave-Fourier analysis were performed for the 2/1-2/1-2/1 approximant $Na_{27}Au_{27}Ga_{31}$ with space group Pa3̅. The square of the Fermi diameter $(2k_{F})^2$, electrons per atom ratio e/a and the critical reciprocal lattice vector $|G|^2$ are determined. A shallow pseudogap at the Fermi level was interpreted as originating from interference of electrons having $(2k_{F})^2$=109.2±1.0 with sets of lattice planes with $|G|^2$'s centered at 108. The effective e/a value for the compound is found to be 1.76 in good agreement with 1.73 derived from a composition average of $(e/a)_{Na}$=1.0, $(e/a)_{Au}$=1.0 and $(e/a)_{Ga}$=3.0.
Źródło:
Acta Physica Polonica A; 2014, 126, 2; 535-538
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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