AI 中文总结
该研究通过第一性原理计算发现Kagome金属CsV₃Sb₅的层间耦合可调控电荷有序波矢，揭示了4×1与2×2电荷有序倾向的关联，为理解其共存竞争提供了统一框架。
AI 中文摘要
Kagome金属AV₃Sb₅中的电荷有序处于包含超导电性、向列性和时间反演对称性破缺迹象的丰富相图中心。然而，哪些电荷有序波矢是本征的、哪些由维度和晶格耦合选择这一基本问题仍未解决。重要的是，不同电荷有序的微观起源，尤其是稳定的体相2×2电荷有序与主要由表面探针解析的有争议4×1调制之间的关系仍未明确。本文中，我们使用第一性原理计算，通过调整层间间距从单层极限到体相极限，研究CsV₃Sb₅中层间耦合的作用。在单层AV₃Sb₅（A=Rb、Cs）中，声子谱在M点无不稳定；相反，主导晶格不稳定出现在q=(1/4,0,0)处，与4×1调制一致。随着CsV₃Sb₅中层间耦合增加，M点声子逐渐软化，在c=12.24 Å附近已变得不稳定，演变为体相特征的强2×2不稳定。这些结果确定，在固定化学计量比下，层间耦合是连接竞争的4×1和2×2倾向的控制参数，为理解Kagome金属中多种电荷有序波矢共存与竞争的原因提供了统一框架。
英文摘要
Charge orders in the kagome metals AV$_3$Sb$_5$ sit at the center of a rich phase diagram that also includes superconductivity, nematicity, and signatures of time-reversal-symmetry breaking. Yet even the basic question of which charge ordering wave vectors are intrinsic, and which are selected by dimensionality and lattice coupling, remains unsettled. Importantly, the microscopic origin of different charge orders and, in particular, the relationship between the robust bulk $2 \times 2$ charge order and the controversial $4 \times 1$ modulation, which is primarily resolved by surface probes, remains unresolved. Here, we use first-principles calculations to study the role of interlayer coupling in CsV$_3$Sb$_5$ by tuning the interlayer separation from the monolayer limit to the bulk limit. In the monolayer AV$_3$Sb$_5$ (A = Rb, Cs), the phonon spectrum exhibits no instability at the M point; instead, the dominant lattice instability occurs at q = (1/4, 0, 0), consistent with a $4 \times 1$ modulation. As interlayer coupling increases in CsV$_3$Sb$_5$, an M-point phonon progressively softens and becomes unstable already near c = 12.24 Å, evolving into the strong $2 \times 2$ instability characteristic of the bulk. These results identify interlayer coupling as a control parameter at a fixed stoichiometry that links competing $4 \times 1$ and $2 \times 2$ tendencies, providing a unified framework for understanding why multiple charge-order wave vectors coexist and compete in kagome metals.
Comments8 pages, 4 figures
