[Wien] Transition probabilities and broadening

[Luigi Maduro]

Hi all,

I have a couple of questions regarding the OPTIC module.

1) I am interested in plotting the transition probability as function of energy to understand the energy loss function of Bi2Te3. As I understood it the imaginary part of the dielectric function is given by

Eps_im(omega, 0) = (constant/omega^2) times | Matrix elements |^2 times JDOS (eq 2.18 on page 20 of the book “Excitation of Plasmons and Interband Transitions by Electrons” by Heinz Raether)

So in principle, I could take the data from Eps_im and divide it by the data in the JDOS file and multiply it by omega^2 (Energy^2 divided by hbar^2), this way I have the transition probabilities as function of energy.
Would this be a correct way of doing it?

Alternatively, I understood that it’s possible to get the symmatrized matrix elements in case.symmat as stated here: https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg04663.html

However, when I look at case.symmat it is not completely clear to me as to how I should interpret the columns in the file, so I would like some help to be clear of the terms. For example the top part of the file has the following output:
------------------------------------------------------------------------------------------------------------
2     Re <X><X>.         Re <Z><Z>                        ALL

KP:        1 NEMIN  NEMAX  :        16       99  dE:       -5.0        3.0   K:                 1

------------------------------------------------------------------------------------------------------------

And then here some columns. My assumption is that Re  <X><X> and  Re <Z><Z> are the squared matrix elements (and so the transition probabilities) along the x-axis and z-axis, respectively. I do not understand what the “ALL” is for and in the second line I am guessing that “KP” means k-point. I am guessing that the NEMIN and NEMAX represent the lowest and highest band levels. dE is then the energy range.
The last column “K:                 1” I am not sure how to interpret, so some assistance on this would be highly appreciated.


2) This question regards the “Gamma: broadening of interband spectrum” that one introduces in the first line of the case.inkram file. Namely, how is this broadening implemented? Is this a Lorentzian broadening? How should I correctly interpret this broadening?


Kind regards,
Luigi Maduro


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