Journal of Physics A Mathematical and General
Triplet order parameter of the triangular Ising model
R. J. Baxter
Abstract
Considers the usual Ising model with pair interactions between nearest-neighbour spins sigma on the triangular lattice. The author evaluates the correlation M 3 =( sigma 1 sigma 2 sigma 3 ), where sigma 1 , sigma 2 , sigma 3 are the three spins at the vertices of a triangular face. This can be thought of as an order parameter associated with a three-spin 'field'. It vanishes at and above T c , and has a critical exponent of 1 / 8 .