Fermi-Hubbard Interaction Quench for Revealing Pair Ordering and Pairing Onset Temperature

The attractive Fermi-Hubbard model is an archetypal model of pairing in quantum many-body systems of fermions. Previously, we experimentally explored the "pseudo-gap" regime, in which the system has full spin pairing at temperatures above the superfluid transition temperature. Depending on the interaction strength, the pair size in this regime varies from tightly bound pairs on a single site to long range pairs with a size approaching the interatomic spacing. By quenching the interaction strength at an appropriate rate, we convert non-local pairs into local pairs without introducing additional pairing or disrupting the long range structure. The observation of local pairs after the interaction quench provides additional evidence for non-local pairing in the attractive Fermi-Hubbard system. Furthermore, using the single-site measurement capabilities of our quantum gas microscope, we detect previously obfuscated charge density wave ordering of the non-local pairs. Finally, conversion of non-local pairs into local pairs allows for lower noise detection of the temperature at which the system becomes fully paired, T*. We exploit this measurement procedure to measure T* over a range of interaction strengths.