Re: [Wannier] Postw90 and Berry curvature origin

2024-01-06 Thread Vahid Askarpour
Dear Professor Vanderbilt,

Thank you for taking the time to respond to my question. I did not realize that 
this question is so involved. Seems like I have a lot of reading to do.

Best,
Vahid

> On Jan 6, 2024, at 4:01 PM, David Vanderbilt  wrote:
> 
> CAUTION: The Sender of this email is not from within Dalhousie.
> 
> Vahid,
> 
> The details are probably complicated, but probably the short answer
> is that Fe is a centrosymmetric collinear magnet.  In this case
> the Berry curvature vanishes everywhere in the BZ in the absence
> of SOC.  Roughly, the SOC goes like L.S which does have an (Lz Sz)
> spin-diagonal component, but typically the (L+ S-) and (L- S+)
> spin-mixing terms are more active.
> 
> I hope this helps a little...
> 
> David
> 
> 
> On Wed, 3 Jan 2024, Vahid Askarpour wrote:
> 
>> Dear Wannier90 Users,
>> 
>> Looking at the postw90 background paper (PRB74, 195118, 2006), in Fig. 3a, 
>> there is a large spike and several small spikes for the Berry curvature in 
>> Fe. The large peak is attributed to spin-orbit coupling with states above 
>> and below E_F. However, both small and large peaks produce small energy 
>> denominators in Eq. 31. This might be obvious to many but  why is the peak 
>> due to spin-orbit much larger than the other peaks?
>> 
>> Thanks,
>> Vahid
>> 
>> Vahid Askarpour
>> Department of Physics and Atmospheric Science
>> Dalhousie University,
>> Halifax, NS
>> CANADA
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>> 
> 
> 
> Prof. David Vanderbilt   Phone: (848) 445-9049
> Department of Physics and Astronomy  Email:  d...@physics.rutgers.edu
> Rutgers University   http://www.physics.rutgers.edu/~dhv
> 136 Frelinghuysen Road
> Piscataway, NJ 08854-8019   USA
> 

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Re: [Wannier] Postw90 and Berry curvature origin

2024-01-06 Thread David Vanderbilt

Vahid,

The details are probably complicated, but probably the short answer
is that Fe is a centrosymmetric collinear magnet.  In this case
the Berry curvature vanishes everywhere in the BZ in the absence
of SOC.  Roughly, the SOC goes like L.S which does have an (Lz Sz)
spin-diagonal component, but typically the (L+ S-) and (L- S+)
spin-mixing terms are more active.

I hope this helps a little...

David


On Wed, 3 Jan 2024, Vahid Askarpour wrote:


Dear Wannier90 Users,

Looking at the postw90 background paper (PRB74, 195118, 2006), in Fig. 3a, 
there is a large spike and several small spikes for the Berry curvature in Fe. 
The large peak is attributed to spin-orbit coupling with states above and below 
E_F. However, both small and large peaks produce small energy denominators in 
Eq. 31. This might be obvious to many but  why is the peak due to spin-orbit 
much larger than the other peaks?

Thanks,
Vahid

Vahid Askarpour
Department of Physics and Atmospheric Science
Dalhousie University,
Halifax, NS
CANADA
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Prof. David Vanderbilt   Phone: (848) 445-9049
Department of Physics and Astronomy  Email:  d...@physics.rutgers.edu
Rutgers University   http://www.physics.rutgers.edu/~dhv
136 Frelinghuysen Road
Piscataway, NJ 08854-8019   USA

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