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Large contribution to Sigma from phonon modes with hv>kB*T
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Joined: Mon Oct 22, 2018 10:31 am
Posts: 20
University: IISER-Pune
Large contribution to Sigma from phonon modes with hv>kB*T
Dear Sir,
I am dealing with a system having 3 atoms/unit cell and therefore, 9 phonon modes with phonon spectrum ranging from 0 to 1000 cm-1.
I am calculating (with verbosity = 3) electron self-energy of the system at 300 K.
I expect that the phonon modes having energy > 0.02585 eV, should have zero contribution to electron self energy because such modes are not excited around 300 K. But looking at the linewidth.elself file tells that some of modes contribute largely to sigma with hv > kB*T. Can you please explain why should it be so?

Wed Dec 11, 2019 2:51 pm

Joined: Mon Oct 22, 2018 10:31 am
Posts: 20
University: IISER-Pune
Re: Large contribution to Sigma from phonon modes with hv>kB
Please respond to this. I am happy provide any information required.
Let me explain my question bit for clearly.
cat linewidth.elself
there are 9 phonon modes and printing electron self-energy@300 K linewidth for ibnd = 3 and ik = 1.
# ik ibnd E(ibnd) imode Im(Sgima)(meV)
1 3 -0.80967953120839E+00 1 0.15081313446142E+00
1 3 -0.80967953120839E+00 2 0.56044872496400E+00
1 3 -0.80967953120839E+00 3 0.54072618258388E+00
1 3 -0.80967953120839E+00 4 0.91195279619482E+00
1 3 -0.80967953120839E+00 5 0.60122838306969E-04
1 3 -0.80967953120839E+00 6 0.17189997097892E+00
1 3 -0.80967953120839E+00 7 0.17606403702447E+00
1 3 -0.80967953120839E+00 8 0.60572097659677E-02
1 3 -0.80967953120839E+00 9 0.26388766112067E+00

My question is , if the phonon spectrum ranges from 0 to 1000 cm-1 and acoustic modes ranges from 0 to 486 cm-1.

Further, 486 cm-1 is equivalent to 700 K. Therefore, the contribution of 6,7 and 9th modes to Sigma should be nearly zero
because bose occupation will be very small for them at lower temperatures (hv > kT).
But what is printed in the output is that modes 6,7,9 are contributing similar to acoustic modes 1,2,3.
Please point out, if I am thinking something wrong.

Sat Dec 14, 2019 4:49 am

Joined: Thu Jan 14, 2016 10:52 am
Posts: 154
University: University of Vienna
Re: Large contribution to Sigma from phonon modes with hv>kB
Hello,

There is also a term in the self-energy corresponding to phonon emission, which can be sizable also at lower temperature.

Carla

Tue Dec 17, 2019 12:50 pm

Joined: Mon Oct 22, 2018 10:31 am
Posts: 20
University: IISER-Pune
Re: Large contribution to Sigma from phonon modes with hv>kB
Thank you for the information.

Mon Jan 13, 2020 7:05 am
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