Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Phase diagram and phase transitions in the system H/Ru(0001): a Monte Carlo study
    Amsterdam : Elsevier
    Surface Science Letters 280 (1993), S. 138-139 
    Details
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0167-2584(93)90801-O
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Phase diagram and phase transitions in the system H/Ru(0001): a Monte Carlo study
    Amsterdam : Elsevier
    Surface Science 280 (1993), S. 185-196 
    Details
    ISSN: 0039-6028
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0039-6028(93)90367-S
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    First excitations of the spin 1/2 Heisenberg antiferromagnet on the kagomé lattice (1998)
    Springer
    The European physical journal 2 (1998), S. 501-507 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models - 75.50.Ee Antiferromagnetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the exact low energy spectra of the spin 1/2 Heisenberg antiferromagnet on small samples of the kagomé lattice of up to N=36 sites. In agreement with the conclusions of previous authors, we find that these low energy spectra contradict the hypothesis of Néel type long range order. Certainly, the ground state of this system is a spin liquid, but its properties are rather unusual. The magnetic ( ) excitations are separated from the ground state by a gap. However, this gap is filled with nonmagnetic ( ) excitations. In the thermodynamic limit the spectrum of these nonmagnetic excitations will presumably develop into a gapless continuum adjacent to the ground state. Surprisingly, the eigenstates of samples with an odd number of sites, i.e. samples with an unsaturated spin, exhibit symmetries which could support long range chiral order. We do not know if these states will be true thermodynamic states or only metastable ones. In any case, the low energy properties of the spin 1/2 Heisenberg antiferromagnet on the kagomé lattice clearly distinguish this system from either a short range RVB spin liquid or a standard chiral spin liquid. Presumably they are facets of a generically new state of frustrated two-dimensional quantum antiferromagnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Free energy and excitation spectrum of a one-dimensional fermi system (1975)
    Springer
    The European physical journal 22 (1975), S. 285-294 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The free energy of a 1-d system of spin 1/2 fermions is studied by means of a perturbation expansion with respect to the spin-flip backward scattering (q ≈ 2k F ) part of the interaction. The perturbation series is analyzed by comparing it with the free energy of a noninteracting quasi fermion system which is characterized by the spectrumε F ± [Δ δ +(υ∥k|−k F |) δ ]1/δ . The connection between the parametersΔ andδ and the coupling constants of the original fermion system is established. A gap in the spin-excitation spectrum is found to exist atT=0 only. The absence of such a gap at finite temperatures is in agreement with the absence of long range order atT ≠ 0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01362252
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The bethe approximation to the three-state chiral clock model (1987)
    Springer
    The European physical journal 66 (1987), S. 227-235 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The three-state chiral clock model is studied by means of the Bethe approximation. While the phase diagram obtained by this method resembles the mean-field phase diagram in the vicinity of the boundary to the paramagnetic phase, a significant improvement is achieved in the low and intermediate temperature regions: By a low-temperature expansion of the free energy, which is carried out to third order, we find that, up to this order, the Bethe approximation exactly reproduces the results of the low-temperature analysis of the full model by Yeomans and Fisher. This and the numerical evaluation of the free energy show that, as far as the longer wavelength phases are concerned, the Bethe approximation is in keeping with predictions of Yeomans and Fisher for low temperature, where mean-field theory is qualitatively misleading. At higher temperatures more complicated structures are found to evolve from the basic low-temperature phases by structure combination branching processes in the same fashion as in the phase diagram of the ANNNI model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01311659
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    TheS=1/2 Heisenberg antiferromagnet on the triangular lattice: Exact results and spin-wave theory for finite cells (1993)
    Springer
    The European physical journal 93 (1993), S. 77-89 
    Details
    ISSN: 1434-6036
    Keywords: 75.10J ; 75.40M
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the ground state properties of theS=1/2 Heisenberg antiferromagnet (HAF) on the triangular lattice with nearest-neighbour (J) and next-nearest neighbour (αJ) couplings. Classically, this system is known to be ordered in a 120° Néel type state for values-∞〈α≦1/8 of the ratio α of these couplings and in a collinear state for 1/8〈α〈1. The order parameter ℳ and the helicity /gC of the 120° structure are obtained by numerical diagonalisation of finite periodic systems of up toN=30 sites and by applying the spin-wave (SW) approximation to the same finite systems. We find a surprisingly good agreement between the exact and the SW results in the entire region-∞〈α〈1/8. It appears that the SW theory is still valid for the simple triangular HAF (α=0) although the sublattice magnetisation ℳ is substantially reduced from its classical value by quantum fluctuations. Our numerical results for the order parameterM of the collinear order support the previous conjecture of a first order transition between the 120° and the collinear order at α≅1/8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01308811
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Influence of nonmagnetic impurities on the kondo effect (1970)
    Springer
    The European physical journal 240 (1970), S. 281-294 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of scattering by nonmagnetic impurities is studied in perturbation theory. While the finite lifetime of the electrons in intermediate states due to scattering by nonmagnetic impurities does not lead to a change in the logT-behaviour of the third-order self-energy, certain vertex-corrections give rise to an additional term which varies like 1/√T at low temperatures. Similar correction terms are found to occur in the higher order self-energy contributions. Although these terms diverge more strongly atT=0 than the logarithmic contributions they are quite small at finite temperatures since they depend on the lifetime τ of the electrons through a factor of (ɛ F τ)−5/2 (ɛ F Fermi energy). The possibility of observing these interference effects experimentally is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01395581
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Impurity states in the excitonic phase (1973)
    Springer
    Journal of low temperature physics 11 (1973), S. 349-361 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of impurities on the excitonic phase is reinvestigated. Treating the scattering of a particle or a hole by an impurity exactly, we find that a single impurity gives rise to a bound state in the energy gap of the excitonic state. For finite concentrations of impurities the superposition of such bound states leads to the formation of an impurity band. The occurrence of such structures in the gap is due to the pair-breaking effect that normal impurities have on the excitonic state. The reduction in the transition temperature caused by impurities is also considered. It is found that the magnitude of the critical concentration at which the excitonic state is completely destroyed depends on the charge of the impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656558
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Effective Hamiltonians for holes in antiferromagnets: a new approach to implement forbidden double occupancy (1998)
    Springer
    The European physical journal 5 (1998), S. 317-324 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models - 71.10.Fd Lattice fermion models - 75.50.Ee Antiferromagnetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A coherent state representation for the electrons of ordered antiferromagnets is used to derive effective Hamiltonians for the dynamics of holes in such systems. By an appropriate choice of these states, the constraint of forbidden double occupancy can be implemented rigorously. Using these coherent states, one arrives at a path integral representation of the partition function of the systems, from which the effective Hamiltonians can be read off. We apply this method to the t-J model on the square lattice and on the triangular lattice. In the former case, we reproduce the well-known fermion-boson Hamiltonian for a hole in a collinear antiferromagnet. We demonstrate that our method also works for non-collinear antiferromagnets by calculating the spectrum of a hole in the triangular antiferromagnet in the self-consistent Born approximation and by comparing it with numerically exact results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050449
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The Heisenberg antiferromagnent on a triangular lattice: A renormalisation group study (1992)
    Springer
    The European physical journal 86 (1992), S. 139-143 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the Heisenberg antiferromagnet in two dimensions on a triangular lattice. Using the coherent state representation for spinS≫1 and performing the spatial continuum limit we arrive at the actionL of a nonlinear σ model. The consituent classical fields ofL are a set of three three-dimensional orthogonal unit vectors. The origin of the symmetrics ofL is uncovered. We investigate this model by a one-loop renormalisation group analysis. In the high temperature limit as well as at zero temperature, the model scales to a fixed point of higher symmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323558
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...