question about excitondb.py

Post here any question you encounter when running the scripts of the yambo-py suite. Post here problem strictly to the python interface as problem coming from the yambo runs should go in the appropriate subforum.

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baiyunfei
Posts: 15
Joined: Thu Dec 01, 2022 12:53 pm

question about excitondb.py

Post by baiyunfei » Sun Mar 12, 2023 1:06 pm

Dear developers
I have a question about the data structure of excitondb.py
From code I excitondb.py, I know I can read exciton wavefunction with yambopy.Exciton eigenvectors are arranged as eigenvectors[i_exc, i_kvc]
Transitions are unpacked in table[ i_k, i_v, i_c, i_s_c, i_s_v ].This works well with q=0 exciton. However,when it comes to q!=0 exciton, the meaning of index i_k becomes vague ,whether it refers to electron momentum or hole momentum?
Best wishes!
Yunfei Bai
Institute of Physics Chinese academy of sciences, Beijing

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palful
Posts: 56
Joined: Tue Jan 26, 2016 11:23 am
Location: Modena and Milan

Re: question about excitondb.py

Post by palful » Mon Mar 13, 2023 10:49 am

Dear Yunfei,

Technically the index "ik" refers to the "electron" momentum.

This depends on the yambo convention for electron-hole transitions: in yambo, an exciton at transfer momentum q is calculated with transitions like (vk' --> ck) where k' = k-q. The index "ik" refers to "k" in this scheme.

Cheers,
Fulvio
Dr. Fulvio Paleari
S3-CNR Institute of Nanoscience and MaX Center
Modena, Italy

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