[Wien] spin polarization of valence states
Peter Blaha
pblaha at theochem.tuwien.ac.at
Tue Dec 11 20:44:25 CET 2007
The QTL-package can give you a decomposition into j=3/2 and 1/2
You need an input file case.cf, and the corresponding splittings are
as tamplates available in SRC_templates/case.cf_* .
For details consult the corresponding UG, but after running qtl-program
you get a case.qtl file with the desired splitting.
Oleg Artamonov schrieb:
> Dear Gerhard,
>
> I work in the cooperation with J. Kirshner and R. Feder. But, please
> come back to my primary question. Let's suppose that due to SO coupling
> we see band splitting in the paramagnetic crystal. Is it possible using
> Wien2k to distinguish which sing of the spin is predominant in each of
> the bands?
> Regards,
> Oleg.
>
>
>
> ----- 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: Tuesday, December 11, 2007 8:37 PM
> Subject: Re: [Wien] spin polarization of valence states
>
>
>> In that case you should consult some basic works:
>> Joachim Kessler "Polarized electrons" (this group did a lot of work on
>> scattering of spin polarized electrons)
>> J¨¹rgen Kirschner "Polarized electrons at surfaces" (who invented the
>> spin detector based on scattering of low energy electrons at tungsten)
>> both published by Springer
>> or
>> R. Feder (ed.) Polarized Electron in Surface Physics, World Scientific
>> Singapore
>>
>> Ciao
>> Gerhard
>>
>> ________________________________________
>> Von: wien-bounces at zeus.theochem.tuwien.ac.at
>> [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Oleg
>> Artamonov [arto at mail.nnz.ru]
>> Gesendet: Dienstag, 11. Dezember 2007 13:42
>> An: A Mailing list for WIEN2k users
>> Betreff: Re: [Wien] spin polarization of valence states
>>
>> Dear Gerhard,
>>
>> We measure the spin-asymmetry of the inelastic scattering of the
>> spin-polarized low energy electron from the valence electron on W single
>> crystal. The more probable origin of the measured spin-asymmetry is the
>> exchange interaction between primary and valence electrons. The SO in the
>> valence states may give the energy splitting in some points of the BZ.
>> For
>> this reason we expect the asymmetry of the spin density of the valence
>> electron in
>> thisi points. To conform this explanation I would like to get from the
>> calculations the SPIN ORIENTATION of the
>> valence electrons in the chosen point of the BZ.
>> For the normal incidence the measured spin-asymmetry changes the sign for
>> symmetry points in the BZ (relative to §¤ point) and that confirms the
>> idea
>> of the SO origin of the spin-asymmetry in the initial state.
>>
>> Best regards,
>> Oleg.
>>
>>
>> ----- 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: Tuesday, December 11, 2007 1:12 PM
>> Subject: Re: [Wien] spin polarization of valence states
>>
>>
>> If you are talking about photoemission experiments, the question is more
>> complicated.
>>
>> You will detect spin polarized electrons even from non polarized initial
>> states, what is basically known as Fano-effect (and its later
>> refinements by
>> Cherepkov).
>> This are truely relativistic effects that are not implemented in Wien2k.
>> Anyway, the spin polarization is in the final state and not in the
>> initial
>> state, it emerges from the optical selection rules (note the photons
>> do not
>> act on the spin but
>> on the total angular momentum). This means you populate the final states
>> with different m_j projection numbers differently even if the initial
>> states had an equal occupation
>> of the m_j quantum numbers.
>> As an example, assume circularly polarised light (The details will become
>> more complicated for linearly polarized ligh (see the work of
>> Heinzmann et
>> al.).
>> This will imply the selection rule Delta m_j=+1 for sigma^+ polarization.
>> If youre initial state is s_1/2,1/2 the final states is p_3/2,3/2 and for
>> s_1/2,-1/2 you have p_1/2,1/2 and p_3/2,1/2
>> immidiately, you see that the final state has not longer an equal
>> distribution of the m_j states.
>> The result is that you have spin polarized electrons, even so the initial
>> state was not polarized at all and had no SO-splitting (|0+1/2| =
>> |0-1/2|).
>> In the same way you will find in emission from the tungsten d-bands
>> polarised electrons, what does NOT mean that the bands are spin polarized
>> anywhere in the BZ.
>> (Following Cherepkov you will find that the effect is even larger due
>> to the
>> SO-splitting of the d-states (indeed not possible for s-states).
>> However, if you calculate the cross section in detail, you find that you
>> need the difference in the final state radial wave functions for p_1/2
>> and
>> p_3/2,
>> otherwise the effect will vanish.
>>
>> You may ask J¨¹rgen Braun (braun at cs.uni-hildesheim.de) he did calculations
>> for W or N.A. Cherepkov (State University of Aerospace
>> Instrumentation, St.
>> Petersburg, Russia)
>> that will give you much more details than I can give here in short. Both
>> will be happy to help you with such questions, just remark that I did
>> send
>> you.
>>
>> Ciao
>> Gerhard
>>
>>
>>
>> ________________________________________
>> Von: wien-bounces at zeus.theochem.tuwien.ac.at
>> [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Oleg Artamonov
>> [arto at mail.nnz.ru]
>> Gesendet: Dienstag, 11. Dezember 2007 09:42
>> An: A Mailing list for WIEN2k users
>> Betreff: Re: [Wien] spin polarization of valence states
>>
>> 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¨C1338 (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.
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
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