[Wien] Questions about imposing external magnetic field on no-magnetic system

[Karel Vyborny]

Yes, SKEAF determines the extremal orbits on the Fermi surface that is 
found by some ab initio calculation (e.g. WIEN2k). The area they enclose 
then enters as A_e in the formula below (and if there are multiple 
extremal orbits then the corresponding dHvA/SdH oscillations are 
superimposed). I judge this from reading README-forSKEAF.txt at

http://susi.theochem.tuwien.ac.at/reg_user/unsupported/SKEAFrelease_v1p3p0_r149.tar.gz

I haven't tried to compile and run. And once again I stress that these 
quantum oscillations are not always observable in actual materials (at 
reasonable magnetic fields).

KV


--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459


On Thu, 27 Jul 2017, Fecher, Gerhard wrote:

> do you search for something like SKEAF by P.M.C. Rourke found in the software goodies ?
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Karel Vyborny [vybornyk at fzu.cz]
> Gesendet: Donnerstag, 20. Juli 2017 21:19
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] Questions about imposing external magnetic field on no-magnetic system
>
> Just one more (extended) comment about the effect of B on band structure:
> it is true that the usual concept of band structure breaks down at |B|>0.
> Something remains (for B||z, E(kz)=h^2*kz^2/2m for free electrons) but
> in any case, the replacement of canonical by kinetic momentum introduces
> quantised levels and (at least some of) continous quantum numbers
> (components of k-vector) are replaced by discrete ones (Landau level
> index). Now, this is what happens to delocalised states (this scenario
> applies e.g. to nearly free electrons) and the opposite (atomic) limit is
> served well (although, strictly speaking this is only an approximation) by
> shifting the orbital levels as described in
>
> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg01508.html
>
> which was mentioned by Gavin, I believe.
>
> On the level of density of states, the effect of B in this limit won't be
> large because the shifts are small. On the other hand, for delocalised
> states (ideally for 2DEG), the smooth (monotonous) g(E) is replaced by
> an oscillatory one (peaks corresponding to positions of Landau levels)
> which depends on the magnitude of B. In some cases (low disorder, low
> DOS), even moderate fields will produce well observable features. When
> Fermi level (Ef) is fixed while B is varied, peaks at Ef come and go
> which leads to de Haas-van Alphen or SdH oscillations periodic in 1/B. The
> period (in units of inverse magnetic flux) equals 4*pi^2/A_e, where A_e
> is the area of extremal cross section of the B=0 Fermi surface
> (perpendicular to B). This is described in detail in Chapter 14 of
> Ashcroft & Mermin.
>
> KV
>
>
>
> --- x ---
> dr. Karel Vyborny
> Fyzikalni ustav AV CR, v.v.i.
> Cukrovarnicka 10
> Praha 6, CZ-16253
> tel: +420220318459
>
>
> On Sun, 16 Jul 2017, Peter Blaha wrote:
>
> ...
>
>> I'm not an expert in in this kind of physics and thus cannot say much
>> more about it, but eg. the anomalous Hall effect can be obtained from
>> the off-diagonal epsilon in spin-orbit optics calculations (Jan Kunes)
>> and the de Haas-van Alphen measurements give you effectively the ground
>> state cross sections of the Fermi surface (one does not even need a
>> magnetic field to calculate this, although experimentally you may even
>> need very large fields to observe these oszillations).
>>
>>
>> Am 16.07.2017 um 10:40 schrieb Karel Vyborny:
>
> ...
>
>>> The fact that Shubnikov-de Haas and de Haas-van Alphen oscillations can
>>> be observed in some bulk solids shows that "strong B" is indeed
>>> achievable. Those 1728 T mentioned below would certainly be strong
>>> enough for many
>>> real systems. However, fields of max. several tesla would not - unless
>>> we deal with a very clean system (like 2DEGs needed for QHE).
>>> Nevertheless, I'd think twice before showing any "band structure with B
>>> switched on" as calculated by WIEN.
>>>
>>> KV
>>>
>>>
>>> --- x ---
>>> dr. Karel Vyborny
>>> Fyzikalni ustav AV CR, v.v.i.
>>> Cukrovarnicka 10
>>> Praha 6, CZ-16253
>>> tel: +420220318459
>>>
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