[QE-users] [Spin Texture]

[Giovanni Cantele]

Hi, if you are dealing with a surface, your system has a
two-dimensional–like band structure as a function of the in-plane momenta
E(kx,ky).

In this case you can:

1) perform a band-structure calculation as you did and plot the bands using
dots whose color and or size are proportional to the x, y, or z component
of the spin;

2) compute the dispersion on a uniform grid sampling the entire Brillouin
zone, plot the energy as a three-dimensional surface as a function of the
two in-plane momentum components, and then, at each point in this
three-dimensional space (kx,ky,E)
draw a vector whose direction is given by the three spin components and
whose magnitude is proportional to the (Sx,Sy,Sz) magnitude. This plot is
for a single band, and in this way you can visualize the full
three-dimensional spin field;

3) compute the dispersion on a uniform grid over the whole Brillouin zone
and plot only the spin texture in two dimensions: at each point in momentum
space draw a vector whose direction is given by the in-plane spin
components (Sx,Sy) and whose length
is proportional to the (Sx,Sy) magnitude, while the arrow color represents
the out-of-plane Sz spin component. On this type of plot you can
superimpose constant-energy contours (for an example, see Fig. 2 of Phys.
Rev. B 110, 165411 (2024),
although many similar examples can be found in the literature).

As for the codes that can produce this kind of plot, there are certainly
some packages where these features are already implemented. Personally, I
usually write this kind of post-processing tools myself, typically in
Python.

Giovanni
-- 

Prof. Giovanni Cantele
Dipartimento di Fisica "Ettore Pancini"
Universita' degli Studi di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at unina.it
Phone: +39 081 676910

Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno mar 13 gen 2026 alle ore 05:16 박기명 <knppkm at naver.com> ha scritto:

> Dear users,
>
> I’d like to hear about your experiences and advice.
>
> I obtained the 2D surface data on the [111] plane using
> calculations='bands' and the crystal_c option. I also used bands.x to
> obtain <Sx>, <Sy>, and <Sz>. However, I faced a problem because data on the
> [111] plane effectively has four components (x, y, z + <Sx> or <Sy> or
> <Sz>), which makes it difficult to plot the spin texture.
>
> Could you recommend a good approach to handle this, or any related
> programs/tools?
>
> Best regards,
> GiMyung Park
> Yonsei University
>
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