Abstract

A combination of exact diagonalization calculations and a well-controlled approximate method is used to study valence and metal-insulator transitions in the spin-one-half Falicov–Kimball model (FKM) in the external magnetic field. It is shown that there exists a critical value of the magnetic field \(h_c\) that depends on the f-level position \(E_f\), above which the spin-one-half FKM maps onto the spinless FKM. In this limit the spin-one-half FKM recovers all physics of the spinless model, including the picture of valence and metal-insulator transitions induced by changes of \(E_f\) and opens the way to its experimental verification in real systems, like rare-earth compounds in the external magnetic field. In addition, we have found that the spin-one-half FKM in the external magnetic field exhibits a wide spectrum of continuous, as well as discontinuous valence, magnetic and metal-insulator transitions that can be induced by tuning directly the external magnetic field or indirectly the external pressure (via the f-level position). The experimental verification of these transitions represent also an interesting challenge, the solution of which can shed more light on the physics of valence and metal-insulator transitions in correlated d-f electron systems. Most of presented results are calculated for the one-dimensional spin-one-half FKM, but to establish connection with the behavior of real rare-earth materials we discuss also effects of the increasing system dimension and the anisotropic spin-dependent d-f interaction, which can play an important role in these materials.

Graphic abstract

中文翻译：

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半自旋Falicov–Kimball模型中的磁场和压力感应的化合价和金属-绝缘体跃迁

摘要

精确的对角化计算和良好控制的近似方法相结合，用于研究外磁场中自旋二分之一的Falicov-Kimball模型（FKM）的化合价和金属-绝缘子跃迁。结果表明，存在磁场的临界值\（h_c \）取决于f级位置\（E_f \），在该临界值上，自旋半FKM映射到无自旋FKM上。在此极限下，半自旋FKM恢复了无旋转模型的所有物理特性，包括由\（E_f \）的变化引起的化合价和金属-绝缘体跃迁的图片并为在真实系统中进行实验验证开辟了道路，例如外部磁场中的稀土化合物。此外，我们发现外部磁场中的自旋半FKM表现出宽范围的连续和不连续的价态，磁性和金属-绝缘体跃迁，可以通过直接调节外部磁场或间接施加外部压力（通过f位置）。对这些跃迁的实验验证也提出了一个有趣的挑战，该问题的解决方案可以更深入地揭示相关d - f的化合价和金属-绝缘体跃迁的物理性质电子系统。大部分给出的结果都是针对一维自旋半二阶FKM计算的，但是为了与真实稀土材料的行为建立联系，我们还讨论了系统尺寸增加和各向异性自旋相关的d - f相互作用的影响，它们可以在这些材料中发挥重要作用。

图形摘要