Random Ising models with transverse field : mean field theory and pair approximation

Osman Canko, Erhan Albayrak, Mustafa Keskín

Osman Canko, Erhan Albayrak

Wei-ji Song, C. Z. Yang

Yu‐qiang Ma, Zhen‐Ya Li

The quantum spin system with a random field has been investigated by combining the pair approximation with the discretized path-integral representation. Second-order transition lines and tricritical points are obtained for the bimodal random-field distributions. Reentrant phase transitions, which may be caused by the competition between quantum effects and the randomness, occur with appropriate ranges of the transverse field and the random field. These results obtained with this approximation are qualitatively different from those of the ordinary mean-field approximation and display that the pair approximation takes into account the local structure of the interaction pattern of the underlying system, which results in coordinate-dependent phase diagrams.

J. R. Drugowich de Felício

Weitao Song, C. Z. Yanc

Abstract The phase diagram and other critical properties of the Ising model of spin‐3/2 in a random transverse field (RTIM) and spin‐5/2 in a transverse field (TIM) are investigated within the approximate scheme which is combined by mean‐field renormalization group theory (MFRG) with the discretized pathintegral representation (DPIR).