[Pw_forum] double delta

[Eyvaz Isaev]

Sorry, but there is a typos:

2) \lambda_{nq} = \gamma_{nq}/(\pi N(e_F)
 \omega_{nq}^2)

according to the first definition (see previous mail)
\lambda_{nq} \to \lambda{qj}, \gamma_{nk} \to
\gamma{qj}, and \omega_{nq} \to \omega_{qj}.

q stands for a wave vector and j is a phonon mode.

Bests,
Eyvaz.

--- Eyvaz Isaev <eyvaz_isaev at yahoo.com> wrote:

> Dear Aritz,
> 
> Please have a look at the next definitions:
> 
> 1) \gamma_{qj} = 2\pi\omega_{qj}
> \sum_{k,n,n'}{|g_{k+q,n';kn}^{qj}|^2 \delta
> (e_{nk}-e_F)\delta (e_{n'`,k+q}-e_F)
> 
> This is so called the phonon linewidth which relates
> two electrons  with different wave vectros (k, and
> k+q) at the Fermi surface.
> |g|^2 is the square of the electron-phonon matrix
> element. 
> 
> 2) \lambda_{nq} = \gamma_{nq}/(\pi N(e_F)
> \omega_{nq}^2)
> 
> I.e. \gamma_{nq} which contains a production of two
> \delta - functions is among main ingridients of the
> electron phonon coupling constant \lambda.
> 
>  
> Bests,
> Eyvaz.
> P.S. My apologies for the previous mail which was
> sent
> accidently. 
> 
> --- Aritz Leonardo <swblelia at sw.ehu.es> wrote:
> 
> > Hello
> > 
> > could anyone tell me what is exactly de meaning of
> > the double_delta in 
> > e-ph calculation?
> > 
> > thanks!
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> 
> 
> 
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