Quantum Simulation of the Unknown: Observation of Pseudogap Physics and Stripes in the Fermi–Hubbard Model

What happens when quantum simulations become cold enough to surprise us? So far, quantum simulations have primarily served as impressive proof-of-principle demonstrations, realizing a wide range of many-body quantum phases. However, temperatures have remained too high to truly access uncharted regimes relevant to strongly correlated quantum materials.

In this talk, we will present a recent breakthrough in which we use an ultracold-atom realization of the Fermi–Hubbard model to explore pseudogap and stripe physics in the doped regime. By achieving a several-fold reduction in temperature, we enter a new regime and observe, unexpectedly, a pronounced peak in the compressibility near 1/8 doping. This feature appears to separate a conventional metallic phase from a pseudogap phase, which we identify by measuring characteristic signatures of the pseudogap in the excitation spectrum. Ongoing work studies the onset of stripe formation. High-precision measurements of spin correlations reveal the formation of 'antiphase domains' of antiferromagnetism characteristic of spin stripes. We also observe an enhanced tendency to break rotational symmetry, compatible with a state of fluctuating stripes.

Altogether, this work represents a key advance in quantum simulation: it demonstrates that we can now address central open questions in condensed matter physics using controlled experiments in regimes that lie at the frontier of classical numerical methods.