Homogeneous fermionic Hubbard gases in flat-top optical lattices

The repulsive fermionic Hubbard model (FHM) is central to our understanding of electron behaviors in strongly correlated materials. At half filling, its ground state is characterized by an antiferromagnetic phase, which is reminiscent of the parent state in high-temperature cuprate superconductors. Introducing dopants into the antiferromagnet, the fermionic Hubbard (FH) system is believed to give rise to various exotic quantum phases, including stripe order, pseudogap, and d-wave superconductivity. We realize a three-dimensional homogeneous fermionic Hubbard gas confined in a hybrid potential, combining a flat-top optical lattice with an optical box trap. In contrast to harmonic or compensating optical lattices, our homogeneous setup provides nearly uniform Hubbard parameters, thereby supporting the emergence of the antiferromagnetic phase. Using spin-sensitive Bragg diffraction of light, we measure the spin structure factor (SSF) of the system. We observe divergences in the SSF by finely tuning the interaction strength, temperature, and doping concentration to approach their respective critical values for the antiferromagnetic phase transition, which are consistent with a power-law scaling in the Heisenberg universality class. Our results pave the way for exploring the low-temperature phase diagram of the FHM.