Lecture
This lecture focuses on deriving the Hamiltonian of an atom in a magnetic field, exploring the paramagnetic and diamagnetic responses. The instructor explains how the canonical momentum influences the base Hamiltonian, considering the kinetic energy and the impact of applying a magnetic field on the canonical momentum. By taking into account the negatively charged electron and the choice of gauge, the final solution is obtained, consisting of the initial Hamiltonian with paramagnetic and diamagnetic contributions.