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  • 1
    Electronic Resource
    Electronic Resource
    Plaquette ground state in the two-dimensional SU(4) spin-orbital model (2000)
    Springer
    The European physical journal 17 (2000), S. 367-370 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models - 11.30.-j Symmetry and conservation laws - 75.40.Mg Numerical simulation studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In order to understand the properties of Mott insulators with strong ground state orbital fluctuations, we study the zero temperature properties of the SU(4) spin-orbital model on a square lattice. Exact diagonalizations of finite clusters suggest that the ground state is disordered with a singlet-multiplet gap and possibly low-lying SU(4) singlets in the gap. An interpretation in terms of plaquette SU(4) singlets is proposed. The implications for LiNiO2 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011085
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  • 2
    Electronic Resource
    Electronic Resource
    RVB description of the low-energy singlets of the spin 1/2 kagomé antiferromagnet (2000)
    Springer
    The European physical journal 17 (2000), S. 651-659 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models - 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) - 75.50.Ee Antiferromagnetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Extensive calculations in the short-range RVB (Resonating valence bond) subspace on both the trimerized and the regular (non-trimerized) Heisenberg model on the kagomé lattice show that short-range dimer singlets capture the specific low-energy features of both models. In the trimerized case the singlet spectrum splits into bands in which the average number of dimers lying on one type of bonds is fixed. These results are in good agreement with the mean field solution of an effective model recently introduced. For the regular model one gets a continuous, gapless spectrum, in qualitative agreement with exact diagonalization results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011071
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetization plateaux and jumps in a class of frustrated ladders: A simple route to a complex behaviour (2000)
    Springer
    The European physical journal 15 (2000), S. 227-233 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models - 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) - 75.45.+j Macroscopic quantum phenomena in magnetic systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the occurrence of plateaux and jumps in the magnetization curves of a class of frustrated ladders for which the Hamiltonian can be written in terms of the total spin of a rung. We argue on the basis of exact diagonalization of finite clusters that the ground state energy as a function of magnetization can be obtained as the minimum - with Maxwell constructions if necessary - of the energies of a small set of spin chains with mixed spins. This allows us to predict with very elementary methods the existence of plateaux and jumps in the magnetization curves in a large parameter range, and to provide very accurate estimates of these magnetization curves from exact or DMRG results for the relevant spin chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510051120
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic properties of the S = 1/2 one-dimensional antiferromagnet MgVO (2000)
    Springer
    The European physical journal 14 (2000), S. 655-659 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Et Exchange and superexchange interactions - 75.30.Cr Saturation moments and magnetic susceptibilities - 75.40.-s Critical-point effects, specific heats, short-range order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The magnetic susceptibility and the electron spin resonance in the X-band of the transition metal oxide compound MgVO3 are reported. We show that this compound, made of weakly coupled infinite chains of VO5 pyramids, behaves as a S =1/2 one-dimensional Heisenberg antiferromagnet. From the ESR and magnetic experiments we deduce the Néel temperature K, the in-chain coupling constant K and the g-factor values g x = g z =1.972(2), g y =1.946(1) for V4+ ions in MgVO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011056
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  • 5
    Electronic Resource
    Electronic Resource
    On the origin of biquadratic exchange in spin 1 chains (2000)
    Springer
    The European physical journal 16 (2000), S. 7-10 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Et Exchange and superexchange interactions - 75.10.Jm Quantized spin models - 75.50.Ee Antiferromagnetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: One-dimensional spin 1 systems may have a rich phase diagram including Haldane gap and dimerized phases if the usually very small biquadratic exchange becomes significant. We show that this unlikely condition may be fulfilled in electron systems with quasi-degenerate orbitals. This mechanism may have been experimentally realized in the spin 1 chain LiVGe2O6. The implications for the exploration of the physics and quantum chemistry of spin 1 chains are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510070242
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  • 6
    Electronic Resource
    Electronic Resource
    Pseudo-gap and possible Spin-Peierls transition in the vanadium oxide VOSb 2 O 4 (2001)
    Springer
    The European physical journal 21 (2001), S. 473-476 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.45.+j Macroscopic quantum phenomena in magnetic systems – 75.50.Ee Antiferromagnetics – 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) – 76.30.-v Electron paramagnetic resonance and relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We report on the magnetic susceptibility and electron spin resonance measurements on polycrystalline samples of the vanadium oxide VOSb2O4, a quasi-one-dimensional S = 1/2 Heisenberg system. The susceptibility vanishes at zero temperature, but there is no cusp at the onset of the susceptibility drop, and the ESR linewidth exhibits an increase characteristic of a phase transition at a much lower temperature. We show that this behaviour is consistent with the formation of a pseudo-gap in a spin-Peierls system in the adiabatic limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011124
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  • 7
    Electronic Resource
    Electronic Resource
    Strain induced correlation gaps in carbon nanotubes (2004)
    Springer
    The European physical journal 38 (2004), S. 9-12 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We calculate the change in the correlation gap of armchair carbon nanotubes with uniaxial elastic strain. We predict that such a stretching will enlarge the correlation gap for all carbon nanotubes by a change that could be as large as several meV per percent of applied strain, in contrast with pure band structure calculations where no change for armchair carbon nanotubes is predicted. The correlation effects are considered within a self-consistent Hartree-Fock approximation to the Hubbard model with on-site repulsion only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00092-2
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  • 8
    Electronic Resource
    Electronic Resource
    Dynamic spin-glass behavior in a disorder-free, two-component model of quantum frustrated magnets (2002)
    Springer
    The European physical journal 26 (2002), S. 301-306 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models – 75.10.Nr Spin-glass and other random models – 75.50.Lk Spin glasses and other random magnets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Motivated by the observation of a spin-glass transition in almost disorder-free Kagome antiferromagnets, and by the specific form of the effective low-energy model of the S = 1/2, trimerized Kagome antiferromagnet, we investigate the possibility to obtain a spin-glass behavior in two-component, disorder-free models. We concentrate on a toy-model, a modified Ashkin-Teller model in a magnetic field that couples only to one species of spins, for which we prove that a dynamic spin-glass behavior occurs. The dynamics of the magnetization is closely related to that of the underlying Ising model in zero field in which spins and pseudo-spins are intimately coupled. The spin-glass like history dependence of the magnetization is a consequence of the ageing of the underlying Ising model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020093
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