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  • 1
    Electronic Resource
    Electronic Resource
    Strong coupling between local moments and superconducting ‘heavy’ electrons in UPd 2 Al 3 (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 410 (2001), S. 340-343 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The electronic structure of heavy-fermion compounds arises from the interaction of nearly localized 4f- or 5f-shell electrons (with atomic magnetic moments) with the free-electron-like itinerant conduction-band electrons. In actinide or rare-earth heavy-fermion materials, this interaction ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35066519
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  • 2
    Electronic Resource
    Electronic Resource
    Quasiclassical Hamiltonians for large-spin systems (2000)
    Springer
    The European physical journal 14 (2000), S. 293-300 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 05.30.-d Quantum statistical mechanics - 75.10.Hk Classical spin models - 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We extend and apply a previously developed method for a semiclassical treatment of a system with large spin S. A multisite Heisenberg Hamiltonian is transformed into an effective classical Hamilton function which can be treated by standard methods for classical systems. Quantum effects enter in form of multispin interactions in the Hamilton function. The latter is written in the form of an expansion in powers of J/(TS), where J is the coupling constant. Main ingredients of our method are spin coherent states and cumulants. Rules and diagrams are derived for computing cumulants of groups of operators entering the Hamiltonian. The theory is illustrated by calculating the quantum corrections to the free energy of a Heisenberg chain which were previously computed by a Wigner-Kirkwood expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050132
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  • 3
    Electronic Resource
    Electronic Resource
    Dielectric response of cylindrical nanostructures in a magnetic field (2000)
    Springer
    The European physical journal 17 (2000), S. 623-627 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 77.22.-d Dielectric properties of solids and liquids - 78.40.Ri Fullerenes and related materials - 75.20.-g Diamagnetism and paramagnetism - 73.23.-b Mesoscopic systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the magnetic field dependence of the dielectric response of large cylindrical molecules such as nanotubes. When a field-induced level crossing takes place, an applied electric field has two effects: it may cause a linear instead of the usual quadratic Stark effect or the difference in the quadratic Stark coefficient of the two levels leads to a discontinuity in the polarization. Explicit calculations are performed for doped nanotubes and a rich structure in the real part of the low-frequency dielectric function is found when a magnetic field is applied along the cylinder axis. It is suggested that studies of can serve as a spectroscopic tool for the investigation of large ring-shaped or cylindrical molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011070
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  • 4
    Electronic Resource
    Electronic Resource
    Low-energy excitations of Yb As in a magnetic field (2000)
    Springer
    The European physical journal 16 (2000), S. 241-244 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.27.+a Strongly correlated electron systems; heavy fermions - 75.30.Ds Spin waves - 75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We discuss the effects of an applied magnetic field on the low-energy excitations in the low temperature phase of Yb4As3. We show also why the magnetic interaction of the Yb3+ ions is nearly of an isotropic Heisenberg spin-1/2 type. A small anisotropy due to an intrachain dipolar interaction leads to the opening of a gap when a magnetic field is applied. The model agrees with available experimental data. Simple experiments are suggested in order to further test the present theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070225
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  • 5
    Electronic Resource
    Electronic Resource
    Structure determination, valence, and superexchange in the dimerized low temperature phase of α ′ - NaV 2 O 5 (2001)
    Springer
    The European physical journal 21 (2001), S. 535-546 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 61.66.Fn Inorganic compounds – 61.50.Ks Crystallographic aspects of phase transformations; pressure effects – 75.30.Et Exchange and superexchange interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report results of a new analysis for the low-temperature structure of α ′ -NaV2O5 from synchrotron X-ray diffraction experiments. We confirm the existence of two inequivalent ladder structures in each vanadium layer. Based on our structural data we perform a bond-valence calculation for the vanadium sites in the low temperature state. Due to an asymmetric charge ordering we obtain only two different vanadium valences despite the three inequivalent sites. This explains the 51V-NMR observation of only two resonant peaks in the charge ordered phase. By use of a Slater-Koster method to obtain hopping matrix elements and cluster calculations we obtain effective vanadium-vanadium hoppings which compare well to LDA results. Using these in a cluster calculation we obtain a superexchange of 0.047 eV between electrons on neighbouring rungs of the same ladder for the undistorted phase. For the distorted phase we find a significant alternation in the shifts of the oxygen atoms along the legs of one of the two ladder types which leads to a significant exchange dimerisation δ J ≈ 0.25.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510170164
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