The free electron model assumes electrons experience a uniform potential. In reality, electrons move through a periodic potential created by the positively charged ion cores. This periodic potential splits the continuous energy spectrum into allowed separated by forbidden band gaps .
Phonons travel as waves through the lattice. Plots of their frequency versus wavevector ( ) yield dispersion curves, which split into: The free electron model assumes electrons experience a
The classic comprehensive textbook: Introduction to Solid State Physics by Charles Kittel . The free electron model assumes electrons experience a
: In semiconductors, photons with energy greater than the bandgap ( The free electron model assumes electrons experience a