[Pw_forum] double delta

[Aritz Leonardo]

thanks a lot for the reply!

Eyvaz Isaev escribió:

>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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