M. Karbach

The frustrated antiferromagnetic Heisenberg model in the presence of a uniform field

On the basis of a numerical computation of the ground states in the sectors with a given total spin S we study the magnetic properties of the one-dimensional frustrated antiferromagnetic Heisenberg model at zero temperature and at the spin-fluid - dimer phase transition. We find that the magnetization curve M(B) has a quartic-root singularity near saturation, . The longitudinal spin - spin, the dimer - dimer and the transverse spin - spin structure factors develop singularities at the field-dependent momenta and , respectively. The type of each of these singularities depends on the frustration parameter and the magnetization M.

SOFT MODES, GAPS, AND MAGNETIZATION PLATEAUS IN ONE-DIMENSIONAL SPIN-1/2 ANTIFERROMAGNETIC HEISENBERG MODELS

We study the one-dimensional spin-1/2 model with nearest and next-to-nearest-neighbor couplings exposed to a homogeneous magnetic field

A numerical study of the formation of magnetisation plateaus in quasi one-dimensional spin-1/2 Heisenberg models

h_{3}

The 1D spin-\(\) AF-Heisenberg model in a staggered field

and a dimer field with period

Critical properties of 1-D spin 1/2 antiferromagnetic heisenberg model

q

Computation of dynamical structure factors with the recursion method

and strength

FROM ONE TO TWO DIMENSIONS IN QUANTUM SPIN SYSTEMS

\delta

Static Structure Factors of the XXZ-Model in the presence of a uniform field

. The latter generates a magnetization plateau at

Opening of a gap in an inhomogeneous external field

M=(1-q/\pi)/2

Approach to the spin-1/2 quantum Heisenberg model

, which evolves with strength