标题： 观察强相互作用费米气体中的空间电荷和自旋关联 显示英文标题

标题： Observing Spatial Charge and Spin Correlations in a Strongly-Interacting Fermi Gas

摘要： 二维关联费米子构成了量子物质的基石，涵盖了广泛的基础和技术领域，并随着现代材料（如高-$T_{\rm c}$超导体、石墨烯、拓扑绝缘体和莫尔结构）的出现吸引了越来越多的兴趣。基于原子的量子模拟器提供了一条理解此类系统核心微观机制的新途径。在这项工作中，我们通过原位探测空间电荷和自旋关联，从微观角度探索了二维吸引费米气体。利用原子分辨的连续量子气体显微镜，我们直接观察到费米子配对，并研究了两点和三点关联函数随自旋间吸引力增加时的演化。测量的精确性使我们揭示了配对关联函数中的显著凹陷，这从根本上被基于巴丁-库珀-施里弗（BCS）理论的平均场结果所禁止，但我们在精确辅助场量子蒙特卡洛计算中确认了其存在。我们证明了BCS预测不仅在超流体交叉区域存在严重不足，而且在弱吸引力一侧也很明显。在测量结果的指导下，我们发现两点和三点关联之间存在显著关系，确立了配对关联的主导作用。最后，利用局部单对损失，我们通过测量谭接触独立表征了配对关联的短程行为，并与数值预测结果取得了极好的一致性。我们的测量为二维费米气体提供了前所未有的微观视角，并为未来连续介质中强关联费米物质的研究带来了范式转变。 显示英文摘要

摘要： Two-dimensional correlated fermions constitute a cornerstone of quantum matter, covering a broad fundamental and technological scope, and have attracted increasing interest with the emergence of modern materials such as high-$T_{\rm c}$ superconductors, graphene, topological insulators, and Moir\'e structures. Atom-based quantum simulators provide a new pathway to understand the microscopic mechanisms occurring at the heart of such systems. In this work, we explore two-dimensional attractive Fermi gases at the microscopic level by probing spatial charge and spin correlations in situ. Using atom-resolved continuum quantum gas microscopy, we directly observe fermion pairing and study the evolution of two- and three-point correlation functions as inter-spin attraction is increased. The precision of our measurement allows us to reveal a marked dip in the pair correlation function, fundamentally forbidden by the mean-field result based on Bardeen-Cooper-Schrieffer (BCS) theory but whose existence we confirm in exact auxiliary-field quantum Monte Carlo calculations. We demonstrate that the BCS prediction is critically deficient not only in the superfluid crossover regime but also deep in the weakly attractive side. Guided by our measurements, we find a remarkable relation between two- and three-point correlations that establishes the dominant role of pair-correlations. Finally, leveraging local single-pair losses, we independently characterize the short-range behavior of pair correlations, via the measurement of Tan's Contact, and find excellent agreement with numerical predictions. Our measurements provide an unprecedented microscopic view into two-dimensional Fermi gases and constitute a paradigm shift for future studies of strongly-correlated fermionic matter in the continuum.