Ground-State Phase Diagram and Magnetization Curves of the Spin-1 Antiferromagnetic Heisenberg Chain with Bond Alternation and Uniaxial Single-Ion-Type Anisotropy

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Ground-state properties of the spin-1 antiferromagnetic Heisenberg chain with bond al-ternation and uniaxial single-ton-type anisotropy, which is described by the Hamiltonian1-to = .)7=.{l - ( -I)'a'jSe - St?n A- D '5'X=. (.5;)' (0.0< cx< 1.0, -(X)< D< oo), are studied.An exact diagonalization method by means of the Lancz6s technique is used. The ground-statephase diagram on the (l' versus D plane at the thermodynamic limit is determined by analyzing the Binder parameters associated with N!el order and z-direction string order for finite-size(.V = 6, 8, - - -, 16) chains. It is found that there exists a multicritical point at which the Haldane,N!el, and singlet-dimer phases meet and that the singlet-dimmer phase and the large-7) phase be-long to the same unique phase. The ground-state magnetization curves at the thermodynamiclimit for various values of a and D are obtained for the system described by the Hamiltonian,-NII7-/g plus the Zeeman term -H p,=. 87. The results show that the 1/2-plateau appears 111 themagnetization curve at least when D >0.0 and 0.0 s cx< 1.0.
社団法人日本物理学会の論文
1996-10-15