CRITICAL PROPERTIES OF XY MODEL ON 2-LAYER TRIANGULAR LATTICE

We investigate phase transitions of the XY model on a two-layer triang ular lattice when interactions are competing, by using Monte Carlo sim ulations. For the system with a ferromagnetic interaction on one of tw o layers and an antiferromagnetic interaction on the other layer, we f ind two different types of critical phenomena with two phase-transitio n temperatures; (1) each of phase transitions due to chirality and (2) the Kosterlitz-Thouless-type phase transition and a chirality transit ion. We clarify the nature of these phase transitions by using finite- size scaling analyses. (C) 1998 Elsevier Science B.V. All rights reser ved.