Journal of the Physical Society of Japan
Correlation Index of the Ising Model with a Transverse Field
Akira Yanase
Abstract
The critical behaviour of the correlation function of the Ising model with a transverse field, Δ , is investigated by means of the perturbation expansions. Exact expressions for the coefficients up to seventh order in J / k T ( J the exchange interaction) are given as functions of Δ / k T for the quadratic, triangular, simple cubic, body-centerd cubic and face-centerd cubic lattices. The universality of the critical index for the correlation length is concluded.