Modified spin-wave theory for the S = 1 frustrated antiferromagnetic Heisenberg chain |
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Authors: | G M Rocha-Filho A ST Pires M E Gouvêa |
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Institution: | 1.Dept. de Fisica, ICEx, Universidade Federal de Minas Gerais,Belo Horizonte,Brazil;2.Centro Federal de Educa??o Tecnológica de Minas Gerais,Belo Horizonte,Brazil |
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Abstract: | We study the one-dimensional isotropic spin-1 Heisenberg
magnet with antiferromagnetic nearest-neighbor (nn) and
next-nearest-neighbor (nnn) interactions by using the modified spin
wave theory (MSWT). The ground state energy and the singlet-triplet
energy gap are obtained for several values of j, defined as the
ratio of the nnn interaction constant to the nn one. We also compare
two different ways of implementing the MSWT currently found in the
literature, and show that, despite the remarkable differences between
the equations to be solved in each procedure, the results given by
both are equivalent, except for the predicted value of the
jmax, the maximum value of j accessible in each treatment.
Here, we suggest that jmax is related to the disorder point of
the first kind. Our results show that the ground state and the gap
energies increase with j, for j ≤jmax, in accordance to
previous numerical results. |
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Keywords: | 75 10 Jm Quantized spin models 75 10 Pq Spin chain models 75 30 Ds Spin waves 75 50 Ee Antiferromagnetics |
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