arXiv:cond-mat/0201174 · Physical Review Letters
Phase Transition in a Two-Dimensional Heisenberg Model
Henk W. J. Blöte, Wenan Guo, Henk J. Hilhorst
Abstract
We investigate the two-dimensional classical Heisenberg model with a nonlinear nearest-neighbor interaction $V(\stackrel{\ensuremath{\rightarrow}}{s},{\stackrel{\ensuremath{\rightarrow}}{s}}^{\ensuremath{'}})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2K[(1+\stackrel{\ensuremath{\rightarrow}}{s}\ifmmode \dot{}\else \.{}\fi{}{\stackrel{\ensuremath{\rightarrow}}{s}}^{\ensuremath{'}})/2{]}^{p}$. The analogous nonlinear interaction for the $\mathrm{XY}$ model was introduced by Domany, Schick, and Swendsen, who find that for large $p$ the Kosterlitz-Thouless transition is preempted by a first-order transition. Here we show that, whereas the standard $(p\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1)$ Heisenberg model has no phase transition, for large enough $p$ a first-order transition appears. Both phases have only short-range order, but with a correlation length that jumps at the transition.