POSSIBILITY OF A CHIRAL PHASE-TRANSITION IN 2D SOLID HE-3

We study a spin system with both two-and four-spin exchange interactio ns on the triangular lattice, which is a possible model for the nuclea r magnetism of solid He-3 layers. We find that a novel phase with scal ar chiral order appears if the four-spin interaction is dominant. Grou nd-state properties are studied using the spin-wave approximation. A p hase transition concerning the scalar chirality occurs at a finite tem perature, since the chirality is an Ising-type variable. Critical phen omena of this transition are studied by Monte Carlo simulations in the classical limit. (C) 1998 Elsevier Science B.V. All rights reserved.