SHG in semimetal system

Questions and doubts about features of non linear optic in Yambo (yamb_nl)

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Belle.X
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Joined: Thu May 19, 2022 6:37 am

SHG in semimetal system

Post by Belle.X » Sat Jun 25, 2022 3:49 pm

Dear Claudio,

Hi, I would like to simulate the SHG properties of WTe2 which is a kind of Type II Weyl Semimetals, and it will be treated as a metallic system in the simulation with Yambo because there is a small overlap of the band structure at about 0.05 eV. However, it seems that the yambo_nl will use covariant dipole methods, which is not implemented for metal.

Followings are some methods that I have tried but cannot help:

1. I used “yambo_nl -V nl” to turn off the ”UseDipoles: Use Covariant Dipoles (just for test purpose)”, in this way, the simulation can proceed but the results are totally strange.

2. I also tried to use the “occupations = fixed” instead of “smearing” to force the system to semiconductor when doing the PWSCF, it helps in monolayer structure with small k points, but it cannot work in a high convergence system and bilayer structure.

3. Moreover, I tried to use shifted k points like “14 14 1 1 1 0” in the PWSCF to get a semiconductor result. However, it cannot help in the bilayer system, and the covariant dipole method cannot implement for shifted k points as well.

Is there other method to do the SHG simulation of the metallic system?

Best Regards,

Yubei

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claudio
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Re: SHG in semimetal system

Post by claudio » Mon Jun 27, 2022 10:37 am

Dear Yubei

in fact the approach implemented in Yambo does not work with metals.

There are two possibilities:

1) you can try with another code, for example 2light
https://etsf.polytechnique.fr/Software/Ab_Initio

2) I can modify yambo_nl to work with shifted grids,
and let you know

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Belle.X
Posts: 3
Joined: Thu May 19, 2022 6:37 am

Re: SHG in semimetal system

Post by Belle.X » Mon Jun 27, 2022 11:30 am

Dear Claudio,

Thank you very much for your suggestion.

I will try with other code first and wait for the modification of yambo_nl.

Thanks again for your help.

Best Regards,

Yubei

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claudio
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Joined: Tue Mar 31, 2009 11:33 pm
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Re: SHG in semimetal system

Post by claudio » Tue Jun 28, 2022 1:18 pm

Dear Yubei

you can use Yambo_nl with shifted grids
if you remove the line

call error(' Shifted grids not implemented yet in covariant dipoles ')

in the file:
src/bz_ops/k_map_nearest_by_dir.F

and then works without symmetries, namely
you put in the QE file

noinv=.true.
nosym=.true.

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

Belle.X
Posts: 3
Joined: Thu May 19, 2022 6:37 am

Re: SHG in semimetal system

Post by Belle.X » Fri Jul 15, 2022 5:33 am

Dear Claudio,

Thank you very much for your help.

I will have a try.

Best Regards,

Yubei

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