中国物理B ›› 2004, Vol. 13 ›› Issue (2): 251-257.doi: 10.1088/1009-1963/13/2/022
R. Quartu1, 堀口刚1, 刘晓彦2, 韩汝琦2, 王漪3
Wang Yi (王漪)ab, R. Quartub, Liu Xiao-Yan (刘晓彦)a, Han Ru-Qi (韩汝琦)a, Horiguchi Tsuyoshi (堀口刚)b
摘要: We investigate phase transitions of the XY model on a two-layer square lattice which consists of a Villain plane (J) and a ferromagnetic plane (I), using Monte Carlo simulations and a histogram method. Depending on the values of interaction parameters (I,J), the system presents three phases: namely, a Kosterlitz-Thouless (KT) phase in which the two planes are critical for I predominant over J, a chiral phase in which the two planes have a chiral order for J predominant over I and a new phase in which only the Villain plane has a chiral order and the ferromagnetic plane is paramagnetic with a small value of chirality. We clarify the nature of phase transitions by using a finite size scaling method. We find three different kinds of transitions according to the values of (I,J): the KT transition, the Ising transition and an XY-Ising transition with ν=0.849(3). It turns out that the Ising or XY-Ising transition is associated with the disappearance of the chiral order in the Villain plane.
中图分类号: (Classical spin models)