BEC-to-BCS crossover from doublon to hole doping in the t’-Hubbard model

by Prof. Fabian Grusdt (LMU Munich)

Wednesday 29 Apr 2026, 10:00 → 11:00 Europe/Zurich

ODRA/111

Understanding the microscopic origins of high-temperature superconductivity and its competition with stripe formation remains a central challenge in strongly correlated physics. Quantum simulation platforms now enable direct access to these phenomena in paradigmatic models such as the Fermi-Hubbard model. Building on this progress, we focus on the extended t′-Hubbard model, which captures key features of correlated cuprates. Using large-scale density-matrix renormalization group (DMRG) simulations and insights from quantum gas microscopy, we investigate the nature of charge carriers and pairing correlations across doublon- and hole-doped regimes. From two-particle spectral functions, which can be accessed in cold-atom experiments, we identify two distinct pairing channels and provide evidence for a continuous BEC-to-BCS crossover as the next-nearest-neighbor tunneling t′ is tuned from positive to negative values. On the BCS side, we observe an emergent instability toward spin-charge stripe formation, revealing the microscopic mechanism behind the competition between superconductivity and stripe order. Our results suggest that the superconducting dome in doped Hubbard systems may be closely tied to a nearby BCS-to-BEC crossover resulting from an emergent Feshbach resonance, pointing to a unifying picture for pairing in strongly correlated fermions and motivating future explorations with quantum simulators and advanced numerical methods.