## On the electrnonic life time and el-ph coupling

Discussion around electron-phonon

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eliephys78
Posts: 82
Joined: Thu May 05, 2016 5:18 pm
Affiliation:

### On the electrnonic life time and el-ph coupling

Dear all,

1- I am in the process of calculating the electronic lifetime (tau) and electron phonon coupling (lambda) for a 2D structure of the form MX2. I am using the electronic k grid crated by EPW (238 points) and converging (tau) w.r.t the q points moving from a qf grif of 30x30x1 to 40x40x1....etc. Since I need one single constant value of (tau), I am calculating the average of tau_{nk} = hbar/ (2 Im \Sigma_{nk}). Tha value I am obtaining is very small something like 3.68471 $\times 10^{-24}$ seconds, which i guess is too small. Is this value reasonale?

2- When calculating both $\lambda$ and $\lambda_{tr}$ for this structure , I am getting 0! The structure is a semi conductor with bandgap ~ 1.5 eV. It makes sense to get small value of $\lambda$ but exactly zero was a bit surprising:

===================================================================
Eliashberg Spectral Function in the Migdal Approximation
===================================================================

lambda : 0.0000000
lambda_tr : 0.0000000

Again, is this reasonable?

Any help or advice would be highly appreciated

Regards
Physics Department
university of Rondonia Brazil
Porto Velho- Rondonia

sponce
Posts: 598
Joined: Wed Jan 13, 2016 7:25 pm
Affiliation: EPFL

### Re: On the electrnonic life time and el-ph coupling

Dear eliephys78,

For 2), yes you should get 0. Indeed the \lambda is compute around the Fermi level only. It is expected to be computed for a metal or doped semiconductor. Therefore if you Fermi level is inside the bandgap, you should get 0

For 1), it depend where you look and at which temperature. It should be non-zero. I'm not sure about what you should expect for 2D materials. Try looking the literature about it. I'm sure scattering rates are reported for MoS2 for example.

Best wishes,
Samuel
Dr. Samuel Poncé
Institute of Materials
École Polytechnique Fédérale de Lausanne (EPFL)
Switzerland
Web: https://www.samuelponce.com

eliephys78
Posts: 82
Joined: Thu May 05, 2016 5:18 pm
Affiliation:

### Re: On the electrnonic life time and el-ph coupling

Dear Samuel,

Regards
Physics Department
university of Rondonia Brazil
Porto Velho- Rondonia

jhosamelly
Posts: 6
Joined: Wed Jul 21, 2021 8:12 am
Affiliation: DLSU

### Re: On the electrnonic life time and el-ph coupling

Hello! I also need to calculate electronic lifetime. Can you please provide the step-by-step process? Thank you.