[论文解读] Superconducting States and Intertwined Orders in Metallic Altermagnets

Xuan Zou, Rafael M. Fernandes+1 more|arXiv (Cornell University)|Mar 4, 2026

Advanced Condensed Matter Physics被引用 0

一句话总结

简要回答：本文分析了d波金属性中性磁性体中多组分等自旋p波超导性，显示两组简并的能隙配对在不同温度下凝聚，并与取向性与自旋电流环涨落交织，形成丰富的相图。

ABSTRACT

Altermagnets are a newly identified class of magnets with nodal spin-split band structures, providing a fertile platform for studying unconventional superconductivity and intertwined orders. Here we investigate multicomponent superconductivity and fluctuation-induced intertwined orders in an interacting $d$-wave metallic altermagnet that is invariant under a combination of a fourfold rotation $C_4$ and time-reversal symmetry $T$. Within mean-field theory, the superconducting ground-state manifold is described in terms of two equal-spin two-component $p$-wave gap functions $(Δ_A^x,Δ_B^y)$ and $(Δ_A^y,Δ_B^x)$, where $A$ and $B$ refer to the two spin-polarized Fermi surfaces related by $C_4T$ symmetry. Because these two sets of gap functions condense at different temperatures, a rich phase diagram with multiple superconducting phase transitions emerges. Distinct fluctuations of sub-leading normal-state instabilities that compete with altermagnetism lift the degeneracy of the multicomponent pairing state in different ways. While nematic fluctuations enhance competition between distinct superconducting components and stabilize nematic superconducting phases, spin current-loop fluctuations promote coexistence and select a pair of chiral states. Our results uncover the pairing structure and elucidate how intertwined sub-leading fluctuations shape superconducting order in altermagnetic metals, suggesting a route toward realizing nematic and topological superconductivity.

研究动机与目标

• 研究在altermagnet中交织序的动机及其对非常规超导性的影响。
• 表征自旋分裂费米面并识别领先的等自旋p波配对通道。
• 建立平均场与勒昂自由能框架以分析多重超导转变和涨落效应。
• 研究取向性与自旋电流环涨落如何与超导性交织，从而稳定取向性或手性拓扑相。

提出的方法

• 构建具有自旋极化带和C4T对称性的d波altermagnetic Lieb晶格模型。
• 计算不同配对通道的超导易度，以识别主导的不稳定性。
• 对每个自旋分量形成两分量的p波序参量，并通过最小化凝聚能得到基态。
• 针对四分量（ΔA/B x/y）序参量展开勒昂自由能，并分析对称性允许的耦合。
• 结合来自取向性与自旋电流环通道的涨落，推导涨落引起的跨带耦合与相行为。

实验结果

研究问题

• RQ1 自旋分裂的altermagnetic费米面更偏好哪些超导配对通道？
• RQ2 两个简并的p波隙集合在不同温度下何以凝聚，形成何种基态结构？
• RQ3 取向性与自旋电流环涨落如何耦合到超导序，并改变量图？
• RQ4 交织的涨落是否能在金属altermagnets中稳定取向性或拓扑超导相？
• RQ5 在这个多分量AM超导体中，副平衡或共存序的条件是什么？

主要发现

• 每个自旋分量内的等自旋p波配对因自旋分裂费米面的存在而被偏好，存在两组简并的隙集合（ΔA^x, ΔB^y）和（ΔA^y, ΔB^x），受C4T对称性约束。
• 两组隙集合通常在不同温度下凝聚，导致多重超导转变和丰富的相图。
• 取向性涨落增强不同超导分量间的竞争，并有利于打破C4T的取向性超导相；而自旋电流环涨落促进共存并选择一对手性态。
• 勒昂理论揭示对称性允许的耦合，使A、B两区序参量交织；涨落引起的项（vAB, vAB^xy, vAB^yx）源自取向性涨落。
• 考虑涨落后，指向在altermagnetic金属中实现取向性与拓扑超导性的可能路径。