Exactly solvable spin ladder model with degenerate ferromagnetic and singlet states
Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Strasse 38, 01187
2 Joint Institute of Chemical Physics of RAS, Kosygin str. 4, 117977 Moscow, Russia
Published online: 15 March 2000
We study the spin ladder model with interactions between spins on neighboring rungs. The model Hamiltonian with the exact singlet ground state degenerated with ferromagnetic state is obtained. The singlet ground state wave function has a special recurrent form and depends on two parameters. Spin correlations in the singlet ground state show double-spiral structure with period of spirals equals to the system size. For special values of parameters they have exponential decay. The spectrum of the model is gapless and there are asymptotically degenerated excited states for special values of parameters in the thermodynamic limit.
PACS: 75.10.Jm – Quantized spin models
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000