Strange absorption spectrum after Post processing using ypp_rt

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Bramhachari Khamari
Posts: 69
Joined: Wed Oct 23, 2019 5:52 am

Strange absorption spectrum after Post processing using ypp_rt

Post by Bramhachari Khamari » Thu Apr 08, 2021 1:07 pm

Dear Developers,
I have done a real time simulation for a material. For a DELTA field and for small field (1000 kw/cm2), My absorption spectrum using ypp_rt looks like equilibrium spectrum. I would like to study the behaviour by applying strong field . For the integrator RK2, NAN value in the polarisation is observed. When I use the following parameters (i-iii) and do the real time calculation. I got the polarisation profile correct. However, ypp_rt does not give the correct absorption spectrum rather it gives a very strange kind.

i) the QSSIN field with field intensity of (4000000 kw/cm2)
ii) Field1_frequncy = excitation frequency from the equilibrium spectrum
iii) Integrator RK4


Other parameter is given below.

Code: Select all

% RTBands
    33 |  52 |                       # [RT] Bands
%
Integrator= "RK4"                # [RT] Integrator. Use keywords space separated  ( "EULER/EXPn/INV" "SIMPLE/RK2/RK4/HEUN" "RWA")
PhLifeTime=100.000000       fs    # [RT] Constant Dephasing Time
RTstep= 0.00100000          fs    # [RT] Real Time step length
NETime=260.000000           fs    # [RT] Simulation Time
% IOtime
 2.000000 | 1.000000 | 0.100000 |  fs    # [RT] Time between two consecutive I/O (CARRIERs - GF - OUTPUT)
%
% Field1_Freq
 0.751000 | 0.75100 |         eV    # [RT Field1] Frequency
%
Field1_Int=4000000.000000       kWLm2 # [RT Field1] Intensity
Field1_Width=43.000000     fs    # [RT Field1] Width
Field1_kind= "QSSIN"              # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
Field1_pol= "linear"               # [RT Field1] Pol(linear|circular)
Any help to get rid of this problem will be appreciated.

Regards,
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

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Davide Sangalli
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Re: Strange absorption spectrum after Post processing using ypp_rt

Post by Davide Sangalli » Sun Apr 11, 2021 3:24 pm

Dear Bramhachari Khamari,
the input parameters look reasonable.

Can you post both the polarization and the absorption spectrum obtained via ypp_rt?

Best,
D.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.oldism.cnr.it/en/davide-sangalli-cv/
http://www.max-centre.eu/

Bramhachari Khamari
Posts: 69
Joined: Wed Oct 23, 2019 5:52 am

Re: Strange absorption spectrum after Post processing using ypp_rt

Post by Bramhachari Khamari » Mon Apr 12, 2021 7:15 am

Dear Davide Sir,
Attached is the pdf file for both polarisation and absorption spectrum. I try to change the integrator from RK4 to EXPn RK4 without success. I got the similar problem. Please help me in this regard to rectify the issue.

Regards,
You do not have the required permissions to view the files attached to this post.
Bramhachari Khamari
Post Doctoral Fellow
Department of Physics
IIT Kanpur, India.

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