how the code treats windows around the Fermi level

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CHILLL
Posts: 45
Joined: Fri Apr 26, 2019 11:39 am
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how the code treats windows around the Fermi level

Post by CHILLL »

Dear experts,

My question is about the code in general, but I will again refer to the paper about LiC6.
I see that for the electron-phonon coupling and the gap distribution (https://ibb.co/8sgFbPS) a window of +-150meV around the Fermi level has been used.
On the other hand, in the anisotropic Elishberg equations the DOS enters as a constant factor, and the DOS within the window of 300 meV is certainly not constant.
Could you please tell me, how is that addressed in the code?

Best regards, Mikhail

roxana
Posts: 164
Joined: Fri Jan 22, 2016 6:48 pm
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Re: how the code treats windows around the Fermi level

Post by roxana »

Hi,

If you would like to learn more about the theory, I recommend you read the "Anisotropic Migdal Eliashberg theory" section from Comp. Phys. Commun. 209, 116 (2016). The anisotropic Eliashberg equations implemented in the code are listed as Eqs. (44) and (45) in the above reference. These equations implicitly assume that the electron DOS is approximately constant near the Fermi energy. This simplification may breakdown for materials with narrow bands or critical points in proximity of the Fermi level.

One way to assess the effect of a variable DOS is to give the Fermi level in the input file. This way the DOS is recalculated based on the new value of the Fermi level. Figure S8 in the supplemental material of PRL 119, 087003 (2017) shows the results following this approach in the case of NbS2.

Best,
Roxana
Roxana Margine
Associate Professor
Department of Physics, Applied Physics and Astronomy
Binghamton University, State University of New York

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