Spin magnetic moments interact with an external magnetic field and acquire energy of U_m=-mu_m . B . Do these moments interact with an applied electric field? If so, how one expresses this energy mathematically? What is that phenomenon?
Fundamentally the E and B fields are the two faces of the same coin. Our way (Stimulus to the nature) of understanding gives us the two different aspects of an entity. In Electron spin magnetic moment, the interaction of the magnetic field with the electron spin provides the two degenerate energy levels. It is the application of the external Electric field after which we can say that they exist!!! The Electron Resonance Spin (ESR) experiment shows us this dynamics.