umklapp process


by aaaa202
Tags: process, umklapp
aaaa202
aaaa202 is offline
#1
Oct30-13, 03:52 PM
P: 991
This occur when two phonons interact and the sum of their momenta add to a new wavevector outside the new Brillioun zone. The resulting wavevector is then mapped back into the Brillioun zone by subtraction of a suitable reciprocal lattice vector.
I don't think I understand the physics in all of this. I understand the idea but what is physically going on in this process and where does the leftover momentum go?
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UltrafastPED
UltrafastPED is offline
#2
Oct30-13, 04:11 PM
Thanks
P: 1,294
The left over energy absorbed by the crystal; the momentum is not "real momentum" - it is crystal momentum, which is not conserved.

See http://www.physicsforums.com/showthread.php?t=715639
DrDu
DrDu is offline
#3
Oct31-13, 01:59 AM
Sci Advisor
P: 3,364
Well, of course also real momentum is conserved. It is taken up completely by the lattice.


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