AI 中文总结
本研究通过两种重整化群方法，改变跳跃参数调控范霍夫奇点，揭示其对关联电子系统有序相的影响，为量子材料设计提供调控规则。
AI 中文摘要
关联电子系统有序相的调控仍是量子材料设计中的核心挑战。电子态密度中的发散点（即范霍夫奇点，VHSs）是实现这种调控的一条明显途径。近期研究表明，这些发散点的精确函数形式会深刻影响所实现的相，但完整的图景仍不清晰。本研究采用热点 parquet 重整化群和截断幺正泛函重整化群，对费米能级处或附近具有范霍夫奇点的二维正方格子哈伯德模型的涌现关联态开展理论研究。通过改变单一跳跃参数 $t_3$，可将态密度中范霍夫奇点的发散强度从对数型（$t_3 < t_{3c}$）变为幂律型（$t_3 = t_{3c}$）；当 $t_3$ 进一步增大（$t_3 > t_{3c}$）时，每个原始范霍夫点会分裂为两个，均为常规对数型。研究表明，所处的参数 regime 强烈影响预测的有序态。此外，还研究了对掺杂的依赖关系，发现这些模型中范霍夫填充时出现的铁磁态对费米能级的微小偏移不稳定，常让位于不同的有序态，具体取决于模型是电子掺杂还是空穴掺杂。这些结果凸显了调控范霍夫奇点性质以控制关联材料中有序态的重要性，并为在新型体系中工程化这些相提供了设计规则。
英文摘要
Controlling the ordered phases of correlated electron systems remains a central challenge in quantum materials design. Divergences in the electronic density of states, known as Van Hove singularities (VHSs), are one obvious route to such control. It is clear from recent work that the exact functional form of these divergences can profoundly affect which phases are realized; a full picture, however, remains elusive. In this work, we use both the hot-spot parquet renormalization group and the truncated-unity functional renormalization group to theoretically study the emergent correlated states of a two-dimensional square-lattice Hubbard model with VHSs at or near the Fermi level. By varying a single hopping parameter, $t_3$, we are able to change the strength of the VHS divergence in the density of states from logarithmic (for $t_3 < t_{3c}$) to power-law (for $t_3 = t_{3c}$). Further increase of $t_3$ ($t_3 > t_{3c}$) causes each original Van Hove point to split into two, both of the conventional logarithmic type. We show that which of these regimes we are in strongly influences the predicted ordered states. We also study the dependence on doping, and find that the ferromagnetic state that occurs at Van Hove filling in these models is unstable to very small shifts in the Fermi level, often giving way to distinct ordered states depending on whether the model is electron- or hole-doped. These results highlight the importance of tuning VHS properties to control ordered states in correlated materials, and offer design rules to engineer these phases in novel systems.
Comments18 pages, 12 figures
