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physica status solidi (b)

Phase Diagram of a Quantum Transverse Spin‐1 Ising Model with Random Fields

Yu‐qiang Ma, Y. G., C. D. Gong

Published Jul 1, 1993• 11 citations
Publisher

Abstract

Abstract The quantum spin‐1 Ising system with random fields is investigated by combining the pair approximation with the discretized path‐integral representation. An analytical expression for the second‐order phase transition is derived for all symmetrical probability distributions of random fields, and phase diagrams for Gaussian and bimodal random fields are obtained numerically.

DOI
10.1002/pssb.2221780121

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Abstract The quantum spin‐1 Ising system with random fields is investigated by combining the pair approximation with the discretized path‐integral representation. An analytical expression for the second‐order phase transition is derived for all symmetrical probability distributions of random fields, and phase diagrams for Gaussian and bimodal random fields are obtained numerically.
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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.
In this paper, we propose a new method, which combines the pair approximation with the discretized path-integral representation, to study the quantum transverse Ising model with random-field. Full phase diagrams are obtained for various random-field distributions. When applied random fields are trimodal (and bimodal), the critical properties including the possibility of the existence of the tricritical points and rcentrance phenomena are numerically analyzed in detail. In the limit z→∞, the extended mean-field result is recovered.