发表机构
Max Planck Institute for the Physics of Complex Systems; Université Côte d’Azur, CNRS, Institut de Physique de Nice (INPHYNI); Department of Physics and Astronomy, University of California, Davis（马克斯·普朗克复杂系统物理研究所; 蔚蓝海岸大学、法国国家科学研究中心、尼斯物理研究所; 加州大学戴维斯分校物理与天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过Holstein模型中的无偏量子蒙特卡洛模拟，揭示了自旋不平衡下有限动量FFLO配对及其与电荷密度波和磁晕的共存现象，为冷原子实验提供了可观测特征。
AI 中文摘要
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) 超导，即由自旋不平衡驱动的有限动量库珀配对，在二维中仍然难以进行数值研究。自旋不平衡吸引Hubbard模型中的费米子符号问题严重限制了量子蒙特卡洛方法在配对关联最显著的低温区域的访问。我们表明，Holstein模型中有效吸引由声子动力学延迟，强烈抑制了自旋不平衡下的符号涨落，使得无偏行列式量子蒙特卡洛模拟能够深入该区域。随着磁化强度增加，零动量配对演变为有限动量FFLO配对，这通过实空间配对关联的振荡和配对磁化率峰位移至有限$\vec{Q}$得以证实。有限动量磁化率显著超过其零动量值。在高密度$n \sim 0.875$、接近磁化强度$m \approx 1-n$（此时多数自旋密度接近半填充）时，FFLO配对与短程棋盘电荷密度波序共存，而交错纵向自旋关联在更大距离上作为磁晕出现。这些空间纹理为有限动量配对提供了实验可观测的特征，并推动了冷原子实现FFLO物理的探索。
英文摘要
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductivity, Cooper pairing at finite-momentum driven by spin imbalance, remains difficult to study numerically in two dimensions. The fermion sign problem in the spin-imbalanced attractive Hubbard model severely limits quantum Monte Carlo access to the low temperatures where pairing correlations are most pronounced. We show that the Holstein model, in which the effective attraction is retarded by phonon dynamics, strongly suppresses sign fluctuations under spin imbalance, enabling unbiased determinant quantum Monte Carlo simulations deep in this regime. With increasing magnetization, zero-momentum pairing evolves into finite-momentum FFLO pairing, evidenced by oscillating real-space pair correlations and a shift of the pairing susceptibility peak to finite $\vec{Q}$. The finite-momentum susceptibility substantially exceeds its zero-momentum value. At high density $n \sim 0.875$, near magnetization $m \approx 1-n$ where the majority-spin density approaches half filling, FFLO pairing coexists with checkerboard charge-density-wave order at short range, while staggered longitudinal spin correlations emerge as a magnetic halo at larger distances. These spatial textures provide experimentally accessible signatures of finite-momentum pairing and motivate cold-atom realizations of FFLO physics.
