- #1
hokhani
- 483
- 8
Transition of an electron from the valence to conduction bands (direct transition at a k-point near the band edge) would change the momentum of electron because the sign of the group velocity in valence and conduction bands are opposite. Could one infer that the direction of radiation is a determining factor in the transition? In other words, by radiating light from a specific direction, if we have transition at k we can not have the same transition at -k because if the radiation could change the group velocity at k from v to -v, it would change the group velocity at -k from -v to -2v while according to band structure the transition at -k requires changing from -v to v!