[Wien] spin polarization of valence states

[Gerhard Fecher]

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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