I can see I was not specific enough in my original post. What I meant was heavy electrons associated with surface plasmons in metal that are an coherent quantum effect. They are called surface plasmon polaritons (SSP). They play an important role in Surface Enhanced Raman Spectroscopy (SERS)...
I want to understand the behavior of heavy electrons. For example is the mass actually changing? If so it would imply that a gravitational field could be affected by an electrical field. I am looking for good understandable references.