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

We study a Hamiltonian of S = 1/2 spins with two-, three and four-spin exchange interactions on the triangular lattice as a possible model o f the nuclear magnetism of solid He-3 layers. The spin wave theory sho ws that the ''tetrahedral'' ground state, which was shown to be favour ed by the four-spin exchange interaction in our previous paper, is sta ble against quantum fluctuations in some parameter region. Since this state has a scalar chiral long-range order, a phase transition occurs at a finite temperature even. though the Hamiltonian has a full rotati onal symmetry in the spin space. critical behavior of this phase trans ition was examined by classical Monte Carlo simulations. The specific heat diverges much more strongly than that of the 2D Ising model.