[Wien] spin polarization of valence states

[Oleg Artamonov]

Dear Gerhard,

Perhaps, I ask my question not completely correct. Of course, the net spin 
polarization  is absent in tungsten.
We measure in the experiment the asymmetry of the spin-up and spin-down 
valence electron density in the chosen point of the BZ. This local 
difference of the spin density is due to the SO interaction.
I would like to get from the calculations the SPIN ORIENTATION of the 
valence electrons in the chosen point of the BZ. How is it possible to 
extract this information (including the sign of the spin)?
Thanks,
                Oleg Artamonov.

----- Original Message ----- 
From: "Gerhard Fecher" <fecher at uni-mainz.de>
To: "A Mailing list for WIEN2k users" <wien at zeus.theochem.tuwien.ac.at>
Sent: Monday, December 10, 2007 11:18 AM
Subject: Re: [Wien] spin polarization of valence states


The SO interaction will split states according to their total angular 
momentum into such with
j=|l+s| and j=|l-s|
this does NOT mean that those states are spin polarised.
To have a net spin polarisation of the density of states one needs an 
unequal occupation of states with different projection quantum number m_s or 
say better m_j=m_l+m_s.
In paramagnetic materials one has no magnetic exchange interaction.
Without exchange interaction - this is the case in W - all states with the 
same absolut value of m_j are equally occupied
(for example the |l,j,m_j> state with |2,5/2,5/2> has always the same 
occupation like the state with |2,5/2,-5/2>)
and therefore one has no spin polarisation anywhere in the BZ of a 
paramagnetic material.

If the question was related to photoemission then check J. Braun, Rep. Prog. 
Phys. 59 (1996) 1267–1338 (and references there) to see how it is still
possible to detect spin polarised "photo"electrons through the selection 
rules.

Ciao
Gerhard


________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at 
[wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Peter Blaha 
[pblaha at theochem.tuwien.ac.at]
Gesendet: Sonntag, 9. Dezember 2007 15:57
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] spin polarization of valence states

Of course in tungsgten even with SO included, the net magnetic moment is
zero and there is no difference between spin-up and dn densities
(integrated over all states of the BZ).
You are also right, SO could give you some splitting of a state at a
certain k-point (leading to possible spin-polarization), but there will
be an equivalent k-point in the BZ where this SO effect is just the
opposite, so in summary the effect is zero.

Oleg Artamonov schrieb:
> Dear Wien users,
>
> Can anybody answer my question. I want to get information about the
> spin-polarization of the valence states. One can expect in the case of
> tungsten the significant energy shift between spin-up and spin-down
> particular states. How is it possible to extract the spin polarization
> state from the result of calculations with the spin-orbit interaction
> taken into account?. I use Wien2k_7.
> Thanks,
>             Oleg Artamonov.
>
>
> ------------------------------------------------------------------------
>
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