Exact models for trimerization and tetramerization in spin chains
Stephan Rachel, Martin Greiter
PHYSICAL REVIEW B | AMER PHYSICAL SOC | Published : 2008
We present exact models for an antiferromagnetic S=1 spin chain describing trimerization as well as for an antiferromagnetic S=3/2 spin chain describing tetramerization. These models can be seen as generalizations of the Majumdar-Ghosh model. For both models, we provide a local Hamiltonian and its exact threefold or fourfold degenerate ground state wave functions, respectively. We numerically confirm the validity of both models using exact diagonalization and discuss the low-lying excitations. © 2008 The American Physical Society.
We would like to thank H.-H. Tu and A.Lauchli for useful discussions. S. R. acknowledges support from the Cusanuswerk.