外场中的哈伯德对簇。磁性研究
Hubbard pair cluster in the external fields. Studies of the magnetic properties
摘要：
本文用严格对角化的哈密顿量方法研究了外电场和磁场作用下的两格点Hubbard团簇的磁性。采用巨正则系综的形式。研究了相图、在位磁化强度、自旋-自旋关联、平均占据数和跳跃能，并以图形说明。温度，平均电子浓度，库仑$U$参数和外部场的影响的数量上的利益。特别是在临界磁场附近发现了磁化强度和关联函数随温度变化的反常行为，并证明了外场的磁化翻转效应。
英文摘要：
The magnetic properties of the two-site Hubbard cluster (dimer or pair), embedded in the external electric and magnetic fields and treated as the open system, are studied by means of the exact diagonalization of the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The phase diagrams, on-site magnetization, spin-spin correlations, mean occupation numbers and hopping energy are investigated and illustrated in figures. An influence of temperature, mean electron concentration, Coulomb $U$ parameter and external fields on the quantities of interest is presented and discussed. In particular, the anomalous behaviour of the magnetization and correlation function vs. temperature near the critical magnetic field is found. Also, the effect of magnetization switching by the external fields is demonstrated.
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