无规场量子Ising模型的研究

本文通过将对近似方法和离散路径积分表示组合,提出一种超越平均场的方法,用来研究无规场存在下的量子横向Ising模型。无规场取不同的形式时对系统相图结构的影响作了统一的描述。无规场取双峰和三峰分布时,通过数值计算对系统的临界特性包括三临界点和重入现象存在的可能性作了详细的研讨。理论在配位数z→∞时退化为平均场结果。关键词：

STUDY OF A QUANTUM TRANSVERSE ISING MODEL WITH RANDOM FIELDS

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.