Comment on 'Ground-State Phase Diagram of the Spin-1/2 Ferromagnetic-Antiferromagnetic Alternating Heisenberg Chains with Anisotropy'

Takashi Tonegawa, Takeshi Nakao, Makoto Kaburagi +3 more

清美 岡本, Kiyomi Okamoto

Kiyomi Okamoto, Dai Nishino

The spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain has been studied by Hida [Phys. Rev. B 46, 8268 (1992)]. We point out an error in his bosonized Hamiltonian representation of this model and also show that his numerical results can be well explained by use of the corrected form of the bosonized Hamiltonian.

Evgeny A. Plekhanov, Adolfo Avella, Francesco Paolo Mancini

清美 岡本, Kiyomi Okamoto

Kazuo Hida

The ground state of the ferromagnetic-antiferromagnetic alternating spin-1/2 Heisenberg chain is studied with Ising-type anisotropy on the ferromagnetic bond. This model tends to the spin-1 antiferromagnetic Heisenberg chain with on-site anisotropy in the limit of strong ferromagnetic bond. It is found that the Haldane-gap phase, the large-D phase, and the two types of N\'eel phases appear as the ground state of this model. The duality relations between these four phases are proved for several limiting cases. The string order parameter characterizing the large-D phase is introduced based on these duality relations. The ground-state phase diagram is determined by the numerical diagonalization of the finite-size system.