arXiv:cond-mat/9809291 · Physical review. B, Condensed matter
Magnetization plateau in the spin ladder with a four-spin exchange
Tôru Sakai, Yasumasa Hasegawa
Abstract
The magnetization process of the $S=1/2$ antiferromagnetic spin ladder with the four-spin cyclic exchange interaction at $T=0$ is studied by the exact diagonalization of finite clusters and size scaling analyses. It is found that a magnetization plateau appears at half the saturation value if the ratio of the four- and two-spin exchange coupling constants ${J}_{4}$ is larger than the critical value ${J}_{4c}=0.05\ifmmode\pm\else\textpm\fi{}0.04.$ The phase transition with respect to ${J}_{4}$ at ${J}_{4c}$ is revealed to be the Kosterlitz-Thouless type.