luminescence calculation

[SAM]

Dear Claudio,

First of all, thank you for your clarification, it helps me a lot. However I still have questions.
please I would like a little more clarification on the interest of studying luminescence assisted by phonon by means of atomic displacement and the interest of studying luminescence by means of exciton-phonon coupling matrix. When to study each of them.

At the level of phonon-assisted luminescence tutorials. When resolving the BSE, what are the places to modify apart from the fact that the number of bands used during the calculation nscf(DFT) must be taken, what value of NGsBlkXs must be taken. I use the yambo 5.2 version. for my initial file I use 40 bands so in total 240 bands.

SAM
PhD student at University of Lome/Togo

[Daniele Varsano]

Dear SAM,

1) atomic displacements or exciton-phonon coupling are two ways to describe the same physics. The interest is on the interpretation of PL experiments presenting phnon replica.

2) Number of bands and dimension of the screening are parameters that are system dependent, and you need to check the convergence.

Best,

Daniele

[SAM]

Dear Claudio,

I want to thank you. Because you gave me more details of understanding.
I will get back to you if I have any further questions.
I submitted a question on the radiative duration of excitons which has still not been answered.
the question was whether it is possible to calculate the lifespan in the following way:
-scf calculation
-nscf calculation
- phonon calculation
- generate the electron-phonon matrix elph_dir
then solve the BSE, and sort the excitons with the command ypp_ph -e s to generate the file o-T0_BSE.exc_qpt1_E_sorted in which I will calculate mu_s^2 by the relation = Maximum Residual Value* Strength

SAM
PhD student at University of Lome

[claudio]

Dear Sam

yes I think it is possible to calculate radiative lifetime of excitons, Maurizia Palummo
did it with Yambo, see for instance here:


https://pubs.acs.org/doi/10.1021/nl503799t

and here

https://arxiv.org/abs/1901.08747

you should ask her directly or try to implement the formula she used in these manuscript

then if you are also interested in exciton-lifetime induced by the coupling with phonons, we are still working on it,
when available we will put it online
or you can use the approximated method described here:
https://www.yambo-code.eu/wiki/index.ph ... emperature

that is already in Yambo.

best
Claudio

[SAM]

Dear claudio,

Thank you once again for your response and details. I am precisely interested in the lifetime of the excitons induced by phonon coupling.
Unfortunately I cannot contact her directly as I do not have these contact details.

I also have another question: is it possible to solve the BSE without calculating the phonon? i.e. without generating the electron-phonon coupling matrix?

Starting from the formula implemented in these articles I had a dimensional analysis problem
for example to calculate gamma:
gamma = (8 * pi *e² *Es(0)*mu_s²)/(hbar * Auc) knowing that: e is the charge of the electron, Es the energy of the excitation in eV, the transition dipole mu_S² in bohr and Auc in cm². What would be the exact dimension of gamma.
starting from file o.exc_qpt1_E_sorted to calculate mu_s² = strength* MaxResidual what would be the dimension of mu_s²
THANKS

PhD student at university of Lomé

[Daniele Varsano]

Dear Sam,
it seems here there is some confusion.

You say you are interested in phonon mediated luminescence, but then your questions are related to papers referring to radiative lifetime.
So it is unclear to what you are interested in.

Best,
Daniele

PS: the contact of Prof. Palummo can be found via a google search

[SAM]

Dear Daniele,

Thank you for your response. There seems to have been a misunderstanding in my previous inquiries. Allow me to clarify my intentions.

I am indeed interested in calculating luminescence, but I am also interested in studying the radiative lifetime of excitons.
thanks
SAM
PhD student

[Daniele Varsano]

Dear Sam,

Ok not it's clear.
Here you have a tutorial for the phonon-assisted luminescence calculation using finite atomic displacements.

https://www.yambo-code.eu/wiki/index.ph ... placements

Best,
Daniele