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  • 1
    Electronic Resource
    Electronic Resource
    Quasiparticle scattering amplitude for normal liquid3He (1983)
    Springer
    Journal of low temperature physics 51 (1983), S. 535-559 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The quasiparticle scattering amplitude is calculated from a semimicroscopic model by analytically solving a generalization of Landau's integral equation to momentum transfers up to 2 PF. This solution in general does not obey exchange symmetry for a given particle-hole irreducible vertex partf pp′(q). We establish conditions for and explicitly construct exchange-symmetric scattering amplitudes by adding higher angular momentum components. Results using certain models forf pp′(q) are compared with transport properties of liquid3He.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00683227
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamical impurity spin susceptibility in metals (1971)
    Springer
    Journal of low temperature physics 5 (1971), S. 575-589 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The longitudinal and transverse impurity spin susceptibilities are expressed exactly in terms of holomorphic self-energies. Within thes-d model these self-energies are calculated in lowest order perturbation theory thus yielding reasonable approximations for the susceptibilities valid for all temperatures and magnetic fields above the Kondo regime and in the whole frequency domain including the hydrodynamical one. The transverse susceptibility and the longitudinal nuclear spin susceptibility are found to be satisfactorily described by Bloch's equations. In the low-temperature regime the longitudinal relaxation timeT 1 exhibits a nontrivial spin and temperature dependence. At low temperatures and high fields the longitudinal localized electron spin susceptibility is found to show a non-Lorentzian double-peak line shape which cannot be described by Bloch's equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628186
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  • 3
    Electronic Resource
    Electronic Resource
    Kondo anomaly of impurity spin resonance linewidth (1970)
    Springer
    The European physical journal 235 (1970), S. 59-65 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the method of Baym and Kadanoff a kinetic equation is derived for the impurity susceptibility in thes-d model. Summing up the most important diagrams the impurity self-energy can be expressed in terms of Suhl'sT-matricest andτ. The contribution of the spin non flip amplitudet to the spin relaxation time is cancelled by a corresponding vertex correction. Thus the final result can be expressed in terms of the spin flip amplitudeτ alone which causes an anomalous temperature dependence of the relaxation time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01399756
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  • 4
    Electronic Resource
    Electronic Resource
    On the static susceptibility in the kondo problem (1970)
    Springer
    The European physical journal 235 (1970), S. 52-58 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamical susceptibility of thes-d-model is calculated in second order. It turns out, that only the impurity-impurity part of the static susceptibility contains logarithmically divergent terms. In order to obtain convergent results belowT=T k a partial summation is carried out for this part. The final result is expressed in terms of Suhl's spin flip scattering amplitude. We find an interpolation formula for the temperature dependence of the susceptibility with complete screening of the impurity spin forS=1/2 atT=0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01399755
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic order and transport in the heavy-fermion system CeCu Au (1998)
    Springer
    The European physical journal 5 (1998), S. 447-455 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Mb Valence fluctuation, Kondo lattice, and heavy-fermion phenomena - 75.25.+z Spin arrangements in magnetically ordered materials - 72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on extensive elastic neutron scattering to determine the wave vector of the magnetic order in CeCu6-xAux single crystals for x 〉 0.1. For all values of x investigated (0.2, 0.3, 0.5, 1.0) we find long-range incommensurate antiferromagnetic order with an ordering vector (0.625 0.275) for x =0.2, nearly unchanged for x =0.3, and (0.59) for x =0.5, staying roughly the same for x =1.0. In addition, short-range correlations are observed for x =0.2, reminiscent of those found previously for x =0.1. The ordered magnetic moment is found to increase rapidly for small x, and more slowly for the larger x values. The increase of the specific-heat anomaly at the ordering temperature with x is in qualitative accord with this behavior. Finally, data of the electrical resistivity for current flow along the three crystallographic directions are presented, showing a clear signature of the magnetic order. A theoretical interpretation of the interplay of magnetic order and transport in terms of (i) the partial suppression of the Kondo effect by the staggered magnetization and (ii) the anisotropic band structure induced by the staggered field is shown to account well for the data, provided the ordering vector is close to 2 k F, where k F is a typical Fermi momentum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050465
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  • 6
    Electronic Resource
    Electronic Resource
    Spin fluctuation contribution to the specific heat of strongly correlated fermions (1990)
    Springer
    The European physical journal 78 (1990), S. 45-50 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the free energy of a system of fermions at low temperatures within the Hubbard model using a slave boson representation, which generalizes the approach of Kotliar and Ruckenstein. The mean field approximation is identical to Gutzwiller's solution. The one-loop corrections provide aT 3 lnT spin fluctuation contribution to the specific heat, which reduces for weak coupling to the result of paramagnon theory first derived by Brenig et al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317355
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  • 7
    Electronic Resource
    Electronic Resource
    Instability of the paramagnetic state towards incommensurate magnetic order in the 2-d Hubbard model (1993)
    Springer
    The European physical journal 90 (1993), S. 297-300 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We determine the instability line separating the paramagnetic phase in the phase diagram of the 2-d Hubbard Model from a phase with incommensurate magnetic order. A mean-field approximation of the Kotliar-Ruckenstein slave boson representation is used to calculate the wave-vector dependent magnetic susceptibility. For largeU/t the instability occurs at a densityn≃0.37, and a wave-vector close toq=(0,π). The dependence ofq onU andn is also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01433051
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  • 8
    Electronic Resource
    Electronic Resource
    Thermally assisted hopping transport in disordered systems (1973)
    Springer
    The European physical journal 258 (1973), S. 381-400 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The response to an external field of localized electrons coupled to phonons is investigated. The low frequency (ω〈T) linear response function is shown to obey a kinetic equation. The transition probabilities (including multiphonon contributions) can be expressed in terms of the dynamical correlation functions(k, ɛ) of the phonons. The low temperature d.c. conductivity in three dimensions obeys a law σ(0)=σ0 · exp(− (T 0/T)1/4). By a combined variational and “nearest neighbor” approximation upper limits for the exponential as well as the pre-exponential factor are obtained. In two dimensions the 1/4 in the exponent has to be replaced by 1/3. The one-dimensional case requires separate considerations which do not simply lead to an exponent 1/2. An expression for the thermopower in the hopping regime is derived and evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01391502
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  • 9
    Electronic Resource
    Electronic Resource
    Theory of thermally assisted electron hopping in amorphous solids (1971)
    Springer
    The European physical journal 246 (1971), S. 1-12 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using a kinetic equation for thermally assisted hopping processes a general expression for the conductivity σ(ω) in disordered systems in terms of the collision operator is derived. The d.c. conductivity is determined by the low lying eigenstates of the collision operator. The eigenvalue equation bears a close analogy to the corresponding problem of atomic vibrations in disordered systems. The calculation of the d.c. conductivity is analogous to the calculation of elastic constants from the dynamical matrix. Using a variational approach for the low lying eigenstates we have found a law In σ(0)=const-(T o/T)1/4. The error in the value ofT o introduced by our trial function has been calculated and found to be reasonably small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402647
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamic response functions of Hubbard model in Gutzwiller approximation (1991)
    Springer
    The European physical journal 82 (1991), S. 369-374 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the two-point dynamic response functions of the Hubbard model at any filling from a slave-boson representation in the paramagnetic saddle point approximation. We use a spin-rotation invariant form of the representation due to Kotliar and Ruckenstein, for which the saddle point corresponds to Gutzwiller's variational approximation. In addition to the spin and charge susceptibilities, which have the familiar RPA form in the limit of small wavevectorq, the double and single-occupancy response functions are here calculated for the first time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357181
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