Question

What does plasmon look like in 3D band structure graph?

Answer 1

Consider metal, and its reciprocal lattice representation with Fermi surface.  What is the correct way to represent a plasmon in this system? M.b. rotating points on the surface? Or 3d membrane-like oscillation of surface? Or what?

Answer 2

$<i>In pure elements, metals is the ordinary case. There are just a few band insulators and those often have the diamond structure (fcc but with two atoms in the primitive cell).$