41 citations · 187 across the 21 of their papers we have counts for
21 papers
Deconfinement phase transition in a two-dimensional model of interacting plaquettes
A. Fledderjohann, A. Klümper, K. H. Mütter
A two-dimensional model of interacting plaquettes is studied by means of the real space renormalization group approach. Interactions between the plaquettes are mediated solely by s…
Real space renormalization group approach to the 2d antiferromagnetic Heisenberg model
A. Fledderjohann, A. Klümper, K. H. Mütter
The low energy behaviour of the 2d antiferromagnetic Heisenberg model is studied in the sector with total spins by means of a renormalization group procedure, which gener…
Instability of isolated triplet excitations on the Shastry-Sutherland lattice (SSL)
A. Fledderjohann, K. -H. Muetter
Configurations of singlets and triplets on the SSL have been proposed in the literature as variational ground states of the Shastry-Sutherland model at fixed magnetization M. We pr…
Magnetic order in the Shastry-Sutherland model
A. Fledderjohann, K. -H. Muetter
The ground state properties of the Shastry-Sutherland model in the presence of an external field are investigated by means of variational states built up from unpaired spins (monom…
The magnetization process in the 2-dimensional J_1-J_2 model
A. Fledderjohann, K. -H. Muetter
We study the alpha = J_2/J_1-dependence of the magnetization process in the J_1-J_2 model on a square lattice with frustrating couplings J_2 along the diagonals. Perturbation expan…
A numerical study of the formation of magnetisation plateaus in quasi one-dimensional spin-1/2 Heisenberg models
R. M. Wiessner, A. Fledderjohann, K. -H. Muetter +1
We study the magnetisation process of the one dimensional spin-1/2 antiferromagnetic Heisenberg model with modulated couplings over j=1,2,3 sites. It turns out that the evolution o…
η-Exponents in the one dimensional antiferromagnetic Heisenberg model with next to nearest neighbour coupling
C. Gerhardt, A. Fledderjohann, E. Aysal +3
We investigate the critical exponents associated with the singularities in the longitudinal and transverse structure factors of the one dimensional antiferroma…
Metamagnetism in the XXZ model with next-to-nearest-neighbor coupling
C. Gerhardt, K. -H. Mütter, H. Kröger
We investigate groundstate energies and magnetization curves in the one dimensional XXZ-model with next to nearest neighbour coupling and anisotropy () at…
Soft modes, Gaps and Magnetization Plateaus in 1D Spin-1/2 Antiferromagnetic Heisenberg Models
A. Fledderjohann, C. Gerhardt, M. Karbach +2
We study the one-dimensional spin-1/2 model with nearest and next-to-nearest-neighbor couplings exposed to a homogeneous magnetic field and a dimer field with period an…
The 1D spin-1/2 AF-Heisenberg model in a staggered field
A. Fledderjohann, M. Karbach, K. -H. Mütter
We investigate the scaling properties of the excitation energies and transition amplitudes of the one-dimensional spin- antiferromagnetic Heisenberg model exposed to an e…
From one to two dimensions in quantum spin systems
A. Fledderjohann, K. -H. Mütter, M. -S. Yang +1
We study the first derivative of the staggered magnetization squared and the second derivative of the ground state energy per site. The parameter $θ…
Critical properties of 1-D spin 1/2 antiferromagnetic Heisenberg model
J. F. Audet, A. Fledderjohann, C. Gerhardt +4
We discuss numerical results for the 1-D spin 1/2 antiferromagnetic Heisenberg model with next-to-nearest neighbour coupling and in the presence of an uniform magnetic field. The m…
The two dimensional antiferromagnetic Heisenberg model in the presence of an external field
M S Yang, K H Mütter
We present numerical results on the zero temperature magnetization curve and the static structure factors of the two dimensional antiferromagnetic Heisenberg model in the presence…
Critical properties of the one-dimensional spin-1/2 antiferromagnetic Heisenberg model in the presence of a uniform field
A Fledderjohann, C Gerhardt, K H Mutter +2
In the presence of a uniform field the one-dimensional spin- antiferromagnetic Heisenberg model develops zero frequency excitations at field-dependent 'soft mode' mome…
Computation of Dynamical Structure Factors with the Recursion Method
A Fledderjohann, M Karbach, K-H Mütter +1
We compute the energies and transition probabilities for low excitations in the one dimensional antiferromagnetic spin-1/2 Heisenberg model by means of the recursion method. We ana…
COMPLETE SOLUTION OF THE XXZ-MODEL ON FINITE RINGS. DYNAMICAL STRUCTURE FACTORS AT ZERO TEMPERATURE.
K. Fabricius, U. Löw, K. -H. Mütter
The finite size effects of the dynamical structure factors in the XXZ-model are studied in the euclidean time -representation. Away from the critical momentum finite siz…
Static Structure Factors of the XXZ-Model in the presence of a uniform field
M. Karbach, K. -H. Mütter, M. Schmidt
The static structure factors of the XXZ model in the presence of uniform field are determined from an exact computation of the groundstates at given total spin on rings with $N=4,6…
Looking at the Haldane Conjecture from a Grouptheoretical Point of View
K. -H. Mütter
Based on the Lieb-Schultz-Mattis construction we present a five parameter family of Spin-1 Hamiltonians with degenerate groundstate. Starting from the critical symmetric Ha…
Finite Size Analysis of the Structure Factors in the Antiferromagnetic XXZ Model
M. Karbach, K. -H. Mütter, M. Schmidt
We perform a finite size analysis of the longitudinal and transverse structure factors in the groundstate of the spin- XXZ model. Comparison with th…
Thermodynamical Properties of the Antiferromagnetic Heisenberg Model in Dimensions d=1,2,3
M. Karbach, K. -H. Mütter, P. Ueberholz +1
The evolution equation for the expectation values of the Boltzmann factor between valence bond states is evaluated in lowest order of the dimer cluster expansion. Explicit formulas…
A New Approach to the Spin 1/2 Quantum Heisenberg Model
K. -H. Mütter
An evolution equation for the expectation values of the Boltzmann factor between monomer valence bond states is derived. It contains the whole information on the thermodynamical an…