Joined: Thu May 05, 2016 5:18 pm Posts: 53
University: Rondonia university

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

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.

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