Masahiro Sato, Naoyuki Watanabe, Nobuo Furukawa
It is known that there is no phase transition down to zero temperature in the antiferromagnetic Ising model on spatially anisotropic triangular lattices, in which the exchange coupling of one direction is stronger than those of other two directions. In the model, the low-temperature physics is governed by domain-wall excitations (defects) residing on bonds of the strong-coupling direction. In this paper, we show that an additional small attractive interaction between defects leads to a Berezinskii-Kosterlitz-Thouless (BKT) transition at a finite temperature, by applying the Monte Carlo simulation. The BKT phase can be viewed as the phase with a quasi long-range order of defects. We determine the phase diagram in a wide parameter regime and argue the phase structure from statistical-mechanics and field-theory viewpoints.
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http://arxiv.org/abs/1305.1403
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