Exciton weight in Yambo-Py

[javad]

Dear Yambo developers

I have a question on YamboPy.

In the tutorial on exciton analysis,
https://wiki.yambo-code.eu/wiki/index.p ... ocal_space

it shown how to plot excitonic weight on the band structure and in the full BZ.
My question is, what exactly is plotted?

For the full BZ I guess:

A_k = \sum_{cv} | A_{cv k} |

and for the band structure

A_{c/v, k} = \sum_{v/c} | A_{cv k} |

is it correct? or it is the sum of the | |^2 ?

best regards
javad

[Daniele Varsano]

Dear Javad,

I'm not an expert on yambo-py, anyway the weights are |Acvk|^2.

Best,

Daniele

[palful]

Dear Javad,

I confirm that it's the square of the weights which is used. This maintains gauge invariance in the case of summing over degenerate exciton states.

Keep in mind that beside the example provided in the tutorial script, you can also construct your own python script to plot exactly the quantities that you want, once read from the yambo databases (via YamboLatticeDB or YamboExcitonDB for example).

Cheers,
Fulvio