Strong-coupling expansion and many-body interpolation approach for strongly correlated systems

Developing accurate and efficient numerical simulation methods for strongly correlated systems remains a central challenge in condensed matter physics. In this talk, we present a new interpolation approach for approximating the Green's function of strongly interacting fields, based on the weak- and strong-coupling expansions. We benchmark this method on two prototypical models—the lattice ϕ4-field and the Hubbard model—and demonstrate that even at very low expansion orders, the interpolation approximants accurately capture the Mott transition and exhibit clear nuermical convergence. We further provide heuristic explanations for the observed convergence using analytic continuation.