ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Ground-state energy of spin-1/2 and spin-1 antiferromagnetic chains: XY model (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5932-5934 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ground-state energy of the XY antiferromagnetic chains with spin-1/2 and spin-1 are obtained by a real space renormalization group method. For S=1/2 a large spin cluster is used in the mapping to improve the accuracy and a boundary theory is applied to extrapolate to the result which is in excellent agreement with the exact Bethe Ansatz result. For S=1 the ground-state energy of the model is obtained by using the renormalization group method and a finite chain calculation for lattices up to 16 sites. The two results are in very good agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342179
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A renormalization group study of the 2D antiferromagnetic Heisenberg model : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6102-6104 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the problem of the existence of long-range staggered magnetic order in the antiferromagnetic Heisenberg model on the square lattice by a renormalization group analysis. We first map the Heisenberg model onto an approximate effective model, described by the Hamiltonian: H = ∑Lj=1S(j)S(j + 1) + ∑Lj=1( − 1)j||J(j)||S(0)S(j), where S(0) represents a single spin located in the center of the ring. We show that the Ji tend to non-zero values as one increases the block size by successive renormalizations, thus establishing the existence of long-range staggered magnetic order in the effective model. We discuss the implications of this result for the original Heisenberg model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352714
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Jahn–Teller effects in the doubly degenerate Hubbard model : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4625-4627 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the Jahn–Teller (JT) effects in the doubly degenerate Hubbard model by using the exact diagonalization (Lanczös algorithm) technique. This is in connection with the newly discovered "colossal magnetoresistance" perovskite-based La1−xAxMnO3 compounds. We first obtain the parameter region where the ground state of the doubly degenerate Hubbard model is ferromagnetically ordered analytically for a dimer, and numerically for larger clusters. Then the effects of static JT distortion in the magnetic ordering of the model are studied numerically. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365184
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Magnetic properties of the lattice Anderson model : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7041-7043 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We perform exact diagonalization studies of the one-dimensional lattice Anderson model for various clusters. The ground state energy and spin–spin correlation functions are calculated as functions of Hubbard U, hybridization V, and f level occupancies. For the symmetric case, we compare our results with weak and strong coupling perturbation theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356719
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Small cluster studies of the lattice Anderson model : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5406-5408 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a numerical calculation of the spectral weight function of the lattice Anderson model for a small cluster. Parameters in the weak hybridization-strong interaction sector are considered. The behavior of the f levels is studied as the f occupancy varies from the doubly occupied limit toward the nearly empty case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353697
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Numerical studies of the quantum spin chain (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5616-5616 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of recent numerical studies of the antiferromagnetic Heisenberg chain with S=1/2, 1, 3/2, and 2. The ground-state energy and the energy gap between the ground state and the first excited state are obtained by using exact diagonalization method on various finite lattices and an improved real-space renormalization method. We discuss our numerical methods and results. Some of our results on the S=1 biquadratic antiferromagnetic model will also be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345902
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Monte Carlo study of the Alexander–Anderson model (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3703-3705 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the Alexander–Anderson model for two magnetic impurities in a metal using a numerical simulation technique. To demonstrate the accuracy of our method we compare simulation results with exact diagonalization results for a two-site conduction band. We study the model as a function of Coulomb interaction u=U/(πΔ)(Δ=hybridization width) and d-level position with respect to the Fermi level εd. We find that correlations between spins are always antiferromagnetic, contrary to predictions of Hartree–Fock and perturbation theory. The consequences of our findings are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338667
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Magnetism in the two-dimensional Hubbard model (abstract) (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3042-3042 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hubbard model has been widely used to describe magnetism due to itinerant electrons. However, except for the one-dimensional case, no exact solution of the model exists. We have studied the two-dimensional Hubbard model on a square lattice using a Monte Carlo simulation technique. Simulations were performed on lattices of up to 8×8 in spatial size. We will discuss results for thermodynamic properties and correlation functions as a function of temperature and interaction strength. For the half-filled band case, our results indicate that the system exhibits long-range antiferromagnetic order in the ground state for any nonzero interaction, although substantially reduced from the classical Néel state due to both charge and spin fluctuations. For the non-half-filled band case, our results suggest that no long-range magnetic order exists. We also don't find any indication of short-ranged ferromagnetic correlations in the parameter range studied. We have also studied the predictions of various approximate treatments for this model, particularly the static approximation and the coherent potential approximation (CPA). By comparison with the Monte Carlo results, we discuss the validity of these schemes. Finally, we discuss the effect of changing the band structure on the magnetic properties of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335207
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Spin-spin correlations in the one-dimensional spin-1/2, antiferromagnetic Heisenberg chain : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5947-5949 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the spin-spin correlations in the ground state of spin-1/2, one-dimensional, antiferromagnetic Heisenberg chain numerically. Using improved algorithms, we have been able to perform exact diagonalizations for lattices up to 30 sites and quantum Monte Carlo simulations for lattices up to 512 sites. This extensive range allows us to investigate the logarithmic dependence of spin-spin correlations. We present our results and discuss their implications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347825
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    On the static approximation for the Hubbard Hamiltonian (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3706-3708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the validity of the static approximation for the Hubbard model. We compare results obtained within the static approximation on two-dimensional finite lattices with results obtained from exact diagonalization and Monte Carlo simulations. We find that the static approximation is quite accurate at high temperatures but breaks down at low temperatures. One reason for its failure is that the static approximation destroys the rotational invariance in spin space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338668
    Location Call Number Expected 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...