Magnetically mediated hole pairing in fermionic ladders of ultracold atoms

Doped antiferromagnets are prime examples of strongly correlated systems and hold the potential to shed light on the emergence of high-T_C superconductivity in cuprate materials via pairing of mobile dopants. Here we report on the microscopic observation of hole pairing due to the magnetic correlations in a Fermi-Hubbard system by using quantum gas microscopy. We prepare two-leg ladders where we disable tunnelling between the rungs in order to suppress Pauli repulsion and thus drastically increase binding energy of the holes. Observing pairs of holes predominantly occupying the same rung of the ladder allows us to extract a binding energy slightly below the superexchange energy. For higher doping levels we find indications of crystallization of hole pairs.