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Andreas Honecker

Publications and source records attributed to Andreas Honecker.

56 records · Page 4Linked to original sources
arXiv2001

Magnetic properties of a spin-1/2 quadrumer chain

We study a novel S=1/2 cluster chain Hamiltonian which has recently been proposed in the context of the charge ordered low-temperature phase of alpha'-NaV2O5. We perform a detailed investigation of this model within a large range of parameters using perturbation theory and Lanczos diagonalization. Using model-specific local conservation laws and parameter-dependent mappings to various effective low-energy Hamiltonians we uncover a rich phase diagram and several regimes of gapful spin-excitations. We find that the overall features of recent neutron scattering data on alpha'-NaV2O5 can be fitted within this model, however using a set of parameters which seems unlikely.

cond-mat.str-el↗
arXiv1995

Quantum Spin Models and Extended Conformal Algebras

First, an algebraic criterion for integrability is discussed -the so-called `superintegrability'- and some results on the classification of superintegrable quantum spin Hamiltonians based on sl(2) are obtained. Next, the massive phases of the Z_n-chiral Potts quantum spin chain (a model that violates parity) are studied in detail. It is shown that the excitation spectrum of the massive high-temperature phase can be explained in terms of n-1 fundamental quasiparticles. We compute correlation functions from a perturbative and numerical evaluation of the groundstate for the Z_3-chain. In addition to an exponential decay we observe an oscillating contribution. The oscillation length seems to be related to the asymmetry of the dispersion relations. We show that this relation is exact at special values of the parameters for general Z_n using a form factor expansion. Finally, we discuss several aspects of extended conformal algebras (W-algebras). We observe an analogy between boundary conditions for Z_n-spin chains and W-algebras and then turn to statements about the structure of W-algebras. In particular, we briefly summarize results on unifying structures present in the space of all quantum W-algebras.

hep-th↗