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  • 1
    Electronic Resource
    Electronic Resource
    Anisotropy of the energy gap in the insulating phase of the U-t-t' Hubbard model (2000)
    Springer
    The European physical journal 18 (2000), S. 241-245 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.10.Fd Lattice fermion models (Hubbard model, etc.) - 71.27.+a Strongly correlated electron systems; heavy fermions - 71.30.+h Metal-insulator transitions and other electronic transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We apply a diagrammatic expansion method around the atomic limit ( ) for the U-t-t ' Hubbard model at half filling and finite temperature by means of a continued fraction representation of the one-particle Green's function. From the analysis of the spectral function we find an energy dispersion relation with a modulation of the energy gap in the insulating phase. This anisotropy is compared with experimental ARPES results on insulating cuprates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070054
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  • 2
    Electronic Resource
    Electronic Resource
    Anisotropic scattering rates and antiferromagnetic precursor effects in the t-t'-U Hubbard model (2000)
    Springer
    The European physical journal 18 (2000), S. 429-433 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.72.-h High-Tc compounds - 75.50.Ee Antiferromagnetics - 79.60.-i Photoemission pacsand photoelectron spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We have investigated the evolution of the electronic properties of the t-t'-U Hubbard model with hole doping and temperature. Due to the shape of the Fermi surface, scattering from short wavelength spin fluctuations leads to strongly anisotropic quasi-particle scattering rates at low temperatures near half-filling. As a consequence, significant variations with momenta near the Fermi surface emerge for the spectral functions and the corresponding ARPES signals. At low doping the inverse lifetime of quasiparticles on the Fermi surface is of order varying linearly in temperature from energies of order t down to a very low energy scale set by the spin fluctuation frequency while at intermediate doping a sub-linear T-dependence is observed. This behavior is possibly relevant for the interpretation of photoemission spectra in cuprate superconductors at different hole doping levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070029
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  • 3
    Electronic Resource
    Electronic Resource
    Nature of the Peierls- to Mott-insulator transition in 1D (2003)
    Springer
    The European physical journal 31 (2003), S. 11-16 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.10.Hf Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems – 71.10.Fd Lattice fermion models (Hubbard model, etc.) – 71.45.Lr Charge-density-wave systems – 71.30.+h Metal-insulator transitions and other electronic transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we analyze ground-state and spectral properties of the one-dimensional half-filled Holstein-Hubbard model using quasi-exact numerical techniques. In the adiabatic limit the transition is connected to the band to Mott insulator transition of the ionic Hubbard model. Depending on the strengths of the electron-phonon coupling and the Hubbard interaction the transition is either first order or evolves continuously across a narrow intermediate phase with finite spin, charge, and optical excitation gaps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00002-2
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal conductivity and thermal Hall effect in Bi- and Y-based high-T c superconductors (2001)
    Springer
    The European physical journal 20 (2001), S. 189-208 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 74.72.-h High Tc compounds – 74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Measurements of the thermal conductivity (kxx) and the thermal Hall effect (kxy) in high magnetic fields in Y- and Bi-based high-T c superconductors are presented. We describe the experimental technique and test measurements on a simple metal (niobium). In the high-T c superconductors kxx and kxy increase below T c and show a maximum in their temperature dependence. kxx has contributions from phonons and quasiparticle (QP) excitations, whereas kxy is purely electronic. The strong increase of kxy below T c gives direct evidence for a strong enhancement of the QP contribution to the heat current and thus for a strong increase of the QP mean free path. Using kxy and the magnetic field dependence of kxx we separate the electronic thermal conductivity ( k xx el ) of the CuO 2 -planes from the phononic thermal conductivity ( k xx ph ). In YBa2Cu3O 7 - δ k xx el shows a pronounced maximum in the superconducting state. This maximum is much weaker in Bi2Sr2CaCu2O 8 + δ , due to stronger impurity scattering. The maximum of k xx el is strongly suppressed by a magnetic field, which we attribute to the scattering of QPs on vortices. An additional magnetic field independent contribution to the maximum of kxx occurs in YBa2Cu3O 7 - δ , reminiscent of the contribution of the CuO-chains, as determined from the anisotropy in untwined single crystals. Our data analysis reveals that below T c as in the normal state a transport (τ) and a Hall ( ) relaxation time must be distinguished: The inelastic (i.e. temperature dependent) contribution to τ is strongly enhanced in the superconducting state, whereas displays the same temperature dependence as above T c . We determine also the electronic thermal conductivity in the normal state from kxy and the electrical Hall angle. It shows an unusual linear increase with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011098
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    Paper (German National Licenses)
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