CeRh2As2的多轨道周期安德森模型
Multiorbital periodic Anderson model for CeRh2As2
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- University of Otago（奥塔哥大学）
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中文总结 AI 辅助
本文针对重费米子超导体CeRh2As2，构建包含准四重态和非对称性的多轨道周期安德森模型，发现其基态主要为金属反铁磁序，为理解其巡游重费米子物理提供了微观基础。
中文摘要 AI 辅助
CeRh2As2是一种重费米子超导体，表现出明显不同的低场和高场超导相，这被广泛解释为反映了序参量宇称的场致变化。然而，超导性在磁性有序附近发展，而磁性有序的微观起源和性质仍不清楚。此外，Ce 4f电子的低位晶体电场分裂的双重态似乎实现了不寻常的“准四重态”结构。这促使人们提出四极自由度在低温物理中起重要作用的建议。在这里，我们发展了CeRh2As2的微观重费米子描述，该描述同时包含了准四重态结构和非对称性。在多轨道周期安德森模型中，我们包含了Ce 4f电子的最低Γ7和Γ6双重态，并允许与导带d电子的非局域杂化。在旋转不变的自旋玻色子形式中强制执行4f态的单占据。采用平均场处理，我们首先表明有效低能哈密顿量可以准确地由单轨道紧束缚模型捕获，这证明了文献中广泛使用的最小描述的合理性。允许磁性基态，我们发现我们的模型在广泛的参数范围内显示出金属Q=(π,π)反铁磁序。铁磁解也会出现，但在较小的参数空间区域内，并且对载流子浓度和f-d杂化形式更敏感。四极矩仅出现在磁有序相内，通常较小，只有当Γ7和Γ6双重态接近简并时才变得显著。我们的结果为理解CeRh2As2的巡游重费米子物理和有序相提供了微观基础。
英文摘要
CeRh2As2 is a heavy-fermion superconductor that exhibits distinct low- and high-field superconducting phases, widely interpreted as reflecting a field-induced change in the parity of the order parameter. However, the superconductivity develops in close proximity to magnetic order whose microscopic origin and nature remain unclear. Moreover, the low-lying crystal-electric-field-split doublets of the Ce 4f electrons appear to realize an unusual "quasi-quartet" structure. This has motivated proposals that quadrupolar degrees of freedom play an important role in the low-temperature physics. Here we develop a microscopic heavy-fermion description of CeRh2As2 that incorporates both the quasi-quartet structure and the nonsymmorphic symmetry. Within a multiorbital periodic Anderson model, we include the lowest-lying $Γ_7$ and $Γ_6$ doublets of the Ce 4f electrons, and allow for nonlocal hybridization with the conduction d electrons. Single occupancy of the 4f states is enforced within the rotationally invariant slave-boson formalism. Adopting a mean-field treatment, we first show that the effective low-energy Hamiltonian is accurately captured by a single-orbital tight-binding model, justifying the minimal descriptions widely employed in the literature. Allowing for a magnetic ground state, we find that our model displays metallic $\mathbf{Q}=(π,π)$ antiferromagnetic order over a wide parameter regime. Ferromagnetic solutions also occur, but in a smaller region of parameter space and with greater sensitivity to carrier concentration and the form of the f-d hybridization. Quadrupolar moments appear only within magnetically ordered phases and are generally small, becoming substantial only when the $Γ_7$ and $Γ_6$ doublets are nearly degenerate. Our results provide a microscopic basis for understanding the itinerant heavy-fermion physics and ordered phases of CeRh2As2.
