Studies of the exactly dimerized bilayer Heisenberg model via strong coupling expansions
Center for Advanced Study, Tsinghua University, Beijing 100084, PR China
2 Institute of Physics, Chinese Academy of Sciences, Beijing 100080, PR China
Revised: 2 July 2000
Published online: 15 November 2000
The one-triplet excitation spectra and thermodynamic properties for the dimerized phase of the frustrated bilayer Heisenberg model are studied using strong-coupling expansion theory. The model has an exact dimerized ground state as well as exact one-triplet excitations in a special case that the frustration J2 is equal to the in-plane coupling J1. We demonstrate that the models with and without frustrations have distinct excitation spectra, so their thermodynamic properties exhibit quite different behaviors. Especially, the low-temperature behaviors of the frustrated model with J1=J2 are independent of the inter-dimer couplings, due to the exact one-triplet excitations.
PACS: 75.10.Jm – Quantized spin models / 75.30.Kz – Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) / 75.40.Cx – Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000