(a) Describe with the aid of diagrams how the free electron dispersion relation is modified by the presence of a periodic potential, and how the electron dynamics change in response to these modifications.
(b) A hypothetical metal has a dispersion relation for its lowest band given by
E = -2A cos(ka).
What is the Fermi energy for a monovalent metal with this dispersion relation?
(c) Calculate the group velocity at the Brillouin zone boundary for this metal.
(d) Find an expression for the effective mass as a function of k for this metal.