Perturbative

Perturbation theory

Controlled expansions in a small parameter — here, hopping over interaction, giving superexchange.

Every topic that uses this method, drawn from across all subjects.

• Strong Coupling: Perturbation Theory and Superexchange Mott Physics in Correlated Lattices In the opposite limit U ≫ t, treating hopping as a perturbation and projecting out doubly occupied sites with a Schrieffer–Wolff transformation maps the half-filled Hubbard model onto the antiferromagnetic Heisenberg model, with superexchange J = 4t²/U.