Effective-Field Theory of Spin Glasses and the Coherent-Anomaly Method. I

Naomichi Hatano, Masuo Suzuki

Naomichi Hatano, Masuo Suzuki

Masuo Suzuki

Overview cluster-variation power-series layered lattices spin glasses quantum percolation, random walk, SAW, DLA... stochastic processes.

Imre Kondor

Alan J. Bray, M A Moore

Yoshihiko Nonomura, Masuo Suzuki

A cluster-effective-field theory, called the double-cluster approximation, is formulated for quantum spin systems at T=0. Combining this approximation with the coherent-anomaly method (CAM), critical phenomena in such systems can be analysed. To test their theory, the authors have estimated the critical points and critical exponents of the one-dimensional S=1/2 transverse Ising model and the one-dimensional S=1/2 XZ model. The estimates are in good agreement with the exact solutions. These results show that the CAM approach is useful in treating zero-temperature phase transitions in quantum spin systems.