Illinois Mobile App Master Calendar

Abstract: Effective model Hamiltonians play an important role in condensed matter physics for the model's simplicity and ability to represent electron interactions. However, deriving an effective model from the electronic ab initio Hamiltonian is difficult, which is why experiment is often used to inform the free parameters in these models. In this talk, I will show principles for downfolding the ab initio Hamiltonian into an effective model. A loss function is used to describe the accuracy retained from the downfolding procedure. I will show results for the Hubbard model computed for a chain of hydrogen atoms and how the best term to extend the model is the next nearest hopping term, which agrees with perturbation theory. This research has two main impacts: first, we can leverage many-body ab initio calculations into more understandable effective models; and second, the state-of-the-art methods of downfolding can be compared to models derived from many-body ab initio calculations.