发表机构
Chen-Ning Yang Institute for Advanced Study (YIAS), Tsinghua University（清华大学陈省身高等研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出动量空间非对称性可促进配对密度波成为弱耦合超导领先不稳定性，并在moiré Chern带中实现拓扑PDW态。
AI 中文摘要
配对密度波（PDW）序是一种具有空间调制序参量的超导态，在传统弱耦合BCS范式中通常次于均匀超导。本文利用扭曲双层棋盘格模型，证明动量空间非对称性提供了一种通用机制，反而能将PDW序提升为领先的弱耦合不稳定性。结合电荷中性点的受控Wilson重整化群分析与有限掺杂的Bethe-Salpeter分析，我们确定了各种竞争不稳定性中的领先有序倾向。在电荷中性点，两个对称相关的二次能带接触点在不同吸引相互作用下支持自旋单重态和自旋三重态PDW不稳定性，而排斥相互作用则有利于量子霍尔绝缘体和有限动量$\mathbf Q$密度波序。掺杂后，非对称性与时间反演共同保护了有限动量$\mathbf Q$配对通道中的Cooper对数在一般填充下成立，使PDW序能在所研究的广泛掺杂范围内保持领先不稳定性。该机制自然扩展到moiré Chern带：通过打破时间反演对称性同时保持非对称性和反演对称性，我们获得了具有BdG Chern数$C_{\text{BdG}}=8$的完全有能隙拓扑自旋三重态PDW态。我们的结果确立了动量空间非对称性作为通往PDW超导（包括拓扑PDW态）的通用弱耦合途径。
英文摘要
Pair-density-wave (PDW) order is a superconducting state with a spatially modulated order parameter and is generally subleading to uniform superconductivity within the conventional weak-coupling BCS paradigm. Here, using a twisted bilayer checkerboard-lattice model, we show that momentum-space nonsymmorphic symmetry provides a generic mechanism that can instead promote PDW order to a leading weak-coupling instability. Combining a controlled Wilsonian renormalization-group analysis at charge neutrality with a finite-doping Bethe--Salpeter analysis, we determine the leading ordering tendencies among various competing instabilities. At charge neutrality, two symmetry-related quadratic band touchings support spin-singlet and spin-triplet PDW instabilities for different attractive interactions, whereas repulsive interactions favor quantum Hall insulators and finite-$\mathbf Q$ density-wave orders. Upon doping, the nonsymmorphic symmetry, together with time reversal, protects the Cooper logarithm in the finite-momentum $\mathbf Q$ pairing channel at generic fillings, allowing PDW order to remain a leading instability over the broad doping range studied. This mechanism extends naturally to moiré Chern bands: by breaking time-reversal symmetry while preserving the nonsymmorphic symmetry and inversion, we obtain a fully gapped topological spin-triplet PDW state with BdG Chern number $C_{\text{BdG}}=8$. Our results establish momentum-space nonsymmorphic symmetry as a general weak-coupling route to PDW superconductivity, including topological PDW states.
Comments30 pages, 7 figures; Supplemental Material included
