What is the momentum of an electron?

iVenky

I was learning about indirect band gap and it says that when the electron comes down from upper energy level to lower energy level it emits photon(which I can understand) but in order to conserve the momentum it emits phonons (which I couldn't understand).

Can you please help me with this?

Thanks a lot.

Naty1

Try wikipedia here:

http://en.wikipedia.org/wiki/Indirect_band_gap

Note the diagrams near the top of the page.....

I don't know much about phonon quasi particles except that they are associated with vibrating structures like lattices.....

Is this your situation??.....read further along in the wiki article and note

[QUOTE]....photons cannot carry crystal momentum,...in an indirect band gap material, the process must also involve the absorption or emission of a phonon, where the phonon momentum equals the difference between the electron and hole momentum.
QUOTE]