HIGH-TEMPERATURE SERIES EXPANSION OF THE FLUCTUATION OF THE VECTOR CHIRALITY FOR THE SPIN-1/2 XY ANTIFERROMAGNET ON THE TRIANGULAR LATTICE

In spin models exhibiting a transition between a low temperature phase with long range chiral order and a high temperature phase without such order, the thermal expectation value of the square of the fluctuation in the chiral order parameter is expected to diverge at the transition temperature. For the spin-1/2 XY antiferromagnet on the triangular lattice a space-type graph high temperature expansion is developed for the fluctuation in the square of the vector chirality operator. Pade approximant analysis of the first six terms of the series yields a pair of complex conjugate poles in the complex K = 1/kT plane, but provides no evidence for a phase transition indicated by a singularity on the real K axis.