Out-of-plane absorption spectrum of a 2D material with a vertical intrinsic electric field

Deals with issues related to computation of optical spectra in reciprocal space: RPA, TDDFT, local field effects.

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WEIW
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Joined: Fri Nov 24, 2017 9:48 am

Out-of-plane absorption spectrum of a 2D material with a vertical intrinsic electric field

Post by WEIW » Mon Oct 18, 2021 10:26 am

Dear Daniele,
I have been bothered by this problem.I have calculated the out-of-plane absorption spectrum of a two-dimensional ferroelectric material, and set the light direction to (0 0 1) and (0 0 -1) respectively. Logically speaking, for these two directions, the absorption intensity is different. However, the absorption spectrums I calculated are the same.
I followed this step to calculate and added the -r to generate a truncated coulomb potential. Step 1: Static screening Step 2: Bethe-Salpeter kernel Step 3: Include previous quasiparticle (GW) results.
I don't know where the problem is,Can you take a look at it for me?
The report file is attached below.

Best wishes,
Liu
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Dr. LIU Hongling
School of Physics, Shandong University
Jinan, CHINA

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Davide Sangalli
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Re: Out-of-plane absorption spectrum of a 2D material with a vertical intrinsic electric field

Post by Davide Sangalli » Mon Oct 18, 2021 11:54 am

Dear Liu,
have calculated the out-of-plane absorption spectrum of a two-dimensional ferroelectric material, and set the light direction to (0 0 1) and (0 0 -1) respectively. Logically speaking, for these two directions, the absorption intensity is different. However, the absorption spectrums I calculated are the same.
As far as I understand eps_{xx}=eps_{-x-x} by definition.
Indeed one computes the dipoles <i|x|j> and then

Code: Select all

eps_{xx} ~ |<i|x|j>|^2 
eps_{-x-x} ~ |-<i|x|j>|^2=|<i|x|j>|^2
~eps_{xx}

How can the two be different?

Best,
D.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
https://sites.google.com/view/davidesangalli
http://www.max-centre.eu/

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