# Quantum gas microscopy of an attractive Fermi-Hubbard system

## TL;DR

This study uses quantum gas microscopy to observe charge-density-wave correlations and superfluidity in an attractive Fermi-Hubbard system, providing insights into pairing phenomena relevant to superconductivity.

## Contribution

It presents the first site-resolved measurements of superfluid correlations and charge-density-wave order in an ultracold atomic Fermi gas simulating the attractive Hubbard model.

## Key findings

- Observation of checkerboard charge-density-wave correlations near half-filling.
- First evidence of superfluid correlations in a single-band Hubbard system of ultracold fermions.
- Charge-density-wave correlations serve as a sensitive thermometer for cooling into superfluid phases.

## Abstract

The attractive Fermi-Hubbard model is the simplest theoretical model for studying pairing and superconductivity of fermions on a lattice. Although its s-wave pairing symmetry excludes it as a microscopic model for high-temperature superconductivity, it exhibits much of the relevant phenomenology, 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. Our site-resolved measurements on the normal state reveal checkerboard charge-density-wave correlations close to half-filling. A "hidden" SU(2) pseudo-spin symmetry of the Hubbard model at half-filling guarantees superfluid correlations in our system, the first evidence for such correlations in a single-band Hubbard system of ultracold fermions. Compared to the paired atom fraction, we find the charge-density-wave correlations to be a much more sensitive thermometer, useful for optimizing cooling into superfluid phases in future experiments.