K.-H. Mütter

Two-spinon dynamic structure factor of the one-dimensional s=1/2 Heisenberg antiferromagnet

The exact expression derived by Bougourzi, Couture, and Kacir for the two-spinon contribution to the dynamic spin structure factor S(q,v) of the one-dimensional s51/2 Heisenberg antiferromagnet at T5 0i s evaluated for direct comparison with finite-chain transition rates (N<28) and an approximate analytical result previously inferred from finite-N data, sum rules, and Bethe ansatz calculations. The two-spinon excitations account for 72.89% of the total intensity in S(q,v). The singularity structure of the exact result is determined analytically and its spectral-weight distribution evaluated numerically over the entire range of the two-spinon continuum. The leading singularities of the frequency-dependent spin autocorrelation function, static spin structure factor, and q dependent susceptibility are determined via sum rules. The impact of the non-twospinon excitations on the integrated intensity, the susceptibility, the frequency moments, and the Euclidian time representation of S(q,v) is studied on the basis of finite-size data. @S0163-1829~97!00517-1#

METAMAGNETISM IN THE XXZ MODEL WITH NEXT-TO-NEAREST-NEIGHBOR COUPLING

We investigate ground-state energies and magnetization curves in the one-dimensional

-exponents in the one-dimensional antiferromagnetic Heisenberg model with next-nearest-neighbour coupling

\mathrm{XXZ}

Diagrammatics for SU(2) invariant matrix product states

model with next-to-nearest neighbor coupling

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

\ensuremath{\alpha}g0

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

and anisotropy

The two dimensional antiferromagnetic Heisenberg model in the presence of an external field

\ensuremath{\Delta}

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

(\ensuremath{-}1l~\ensuremath{\Delta}l~1)

Instability of isolated triplet excitations on the Shastry-Sutherland lattice

at