[Pw_forum] Semi-Metallic behavior in semi-conductor superlattice;

[Zahra Taghipour]

Dear Developers and Users,

I have a conceptual question:
I am working on a semi-conductor superlattice that has an experimental Gamma-to-Gamma transition of 280 meV.
On the other hand, I am trying to simulate this structure within DFT using QE to study the excitons (to be corrected with GW).
What I see is a semi-metalic behavior: highest occupied is at Gamma, and lowest unoccupied is at the border of BZ and lower than highest occupied at Gamma. This behavior is seen for couple of different PP’s.
GW corrects Gamma-to-Gamma transition pretty well, which it is very close to the experiment; But, the semimetal behavior is still present.
So, here is my question:

Lets’ say the Temperature is low. Experimentally, one excites the electron at Gamma (correct?), therefore, how one sees the semi-metal effect in the experiment (Where does the fact that there is a k-point in the border that has lower unoccupied state than the highest Gamma show itself in the experiment?

I realize that my question is probably above the scope of this forum, but I hope to find the answer to my confusion from the experts in the forum.
Any comment is really appreciated.

Yours

Zahra
PhD student, Center for High Technology Materials, Univ. of New Mexico, USA