The attractive Fermi–Hubbard model is the simplest theoretical model for studying pairing and superconductivity of fermions on a lattice. It exhibits many interesting features including a short-coherence length at intermediate coupling and a pseudogap regime with anomalous properties. Here we study an experimental realization of this model using a two-dimensional (2D) atomic Fermi gas in an optical lattice. Using a new technique for selective imaging of doublons with a quantum gas microscope, we observe chequerboard doublon density correlations in the normal state close to half-filling. With the aid of quantum Monte Carlo simulations, we show that the measured doublon density correlations allow us to put a lower bound on the strength of s-wave pairing correlations in our system. We compare the temperature sensitivity of the doublon density correlations and the paired atom fraction and find the correlations to be a much better thermometer. Accurate thermometry of attractive lattice systems will be essential in the quest for optimizing cooling schemes to reach superfluid phases in future experiments.

有吸引力的费米-哈伯德模型是研究费米子在晶格上的配对和超导性的最简单的理论模型。它表现出许多有趣的特征，包括中间耦合处的短相干长度和具有异常性质的伪间隙机制。在这里，我们使用光学晶格中的二维（2D）原子费米气体研究该模型的实验实现。使用一种新的技术，用量子气体显微镜对杜宾犬进行选择性成像，我们在接近半填充状态的正常状态下观察棋盘格杜宾犬密度的相关性。借助量子蒙特卡洛模拟，我们表明，测得的双链密度相关性使我们能够将s的强度设置为下限我们系统中的波配对相关性。我们比较了双密度密度相关性和成对的原子分数的温度敏感性，发现该相关性是一个更好的温度计。有吸引力的晶格系统的准确测温对于优化冷却方案以在未来的实验中达到超流体相至关重要。