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Mean-field theory for Heisenberg zigzag ladder: Ground state energy and spontaneous symmetry breaking

V. V. Mkhitaryan·T. A. Sedrakyan
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Abstract

The spin-1/2 zig-zag Heisenberg ladder (J_1 - J_2 model) is considered. A new representation for the model is found and a saddle point approximation over the spin-liquid order parameter < \vec σ_{n-1}(\vec σ_{n}\times \vec σ_{n+1}) > is performed. Corresponding effective action is derived and analytically analyzed. We observe the presence of phase transitions at values J_2/J_1=0.231 and J_2/J_1=1/2.

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V. V. Mkhitaryan, T. A. Sedrakyan. 2006-11-03. Mean-field theory for Heisenberg zigzag ladder: Ground state energy and spontaneous symmetry breaking. https://doi.org/10.1007/s00023-006-0294-4

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