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I have plotted ContourPlot3D of fermi surface

e2[kx_, ky_, kz_] = 
 1/3 (2 (Cos[Sqrt[3] kx] + 2 Cos[(Sqrt[3] kx)/2] Cos[(3 ky)/2]) Cos[
      3 kz] + Sqrt[
    9 Abs[E^(-(1/2) I (Sqrt[3] kx - ky)) + E^(-I ky) + E^(
        1/2 I (Sqrt[3] kx + ky))]^2 + (3 + 
       4 (-Cos[(Sqrt[3] kx)/2] + Cos[(3 ky)/2]) Sin[(Sqrt[3] kx)/
         2] Sin[3 kz])^2])
ContourPlot3D[e2[kx, ky, kz] == 
  0, {kx, (-4 \[Pi])/(3 Sqrt[3] a), (4 \[Pi])/(
  3 Sqrt[3] a)}, {ky, (-2 \[Pi])/(3 a), (2 \[Pi])/(3 a)}, {kz, -\[Pi]/
  c, \[Pi]/c}, AxesLabel -> Automatic]

enter image description here

The Brillouin zone looks like the 3D hexagonal lattice enter image description here

How can I show the Fermi surface on the the above Hexagonal lattice? (Parameters a=1 and c=3)

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    $\begingroup$ You can use this: p = ContourPlot3D[...]; r = \[Pi]/a; h = -\[Pi]/c; \[Phi] = 0; hexP = CirclePoints[{r, \[Phi]}, 6]; hex = ConvexHullRegion[(Append[#, -h] & /@ hexP)~ Join~(Append[#, h] & /@ hexP)]; Show[Graphics3D[{EdgeForm[Black], FaceForm[None], hex}], p] However, you have to adjust r, h and \[Phi] because I don't know how exactly they relate to your parameters a, b and c. $\endgroup$
    – Domen
    Aug 11, 2021 at 15:19
  • $\begingroup$ @Domen I ran the code you sent with appropriate parameters, but its giving an error that "ConvexHullRegion is not a Graphics3D primitive or directive" $\endgroup$
    – sslucifer
    Aug 11, 2021 at 15:36
  • $\begingroup$ Can you provide us the appropriate parameters, please? $\endgroup$
    – Domen
    Aug 11, 2021 at 15:49
  • $\begingroup$ @Domen I have edited the post with parameters. I hope that should be enough. If you can show me that you are that you are able to make a 3D hexagon. I think that should answer my question. $\endgroup$
    – sslucifer
    Aug 11, 2021 at 16:03
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    $\begingroup$ I see it now, you are probably using an older version of Mathematica. Replace ConvexHullRegion with ConvexHullMesh in my code. $\endgroup$
    – Domen
    Aug 11, 2021 at 16:05

1 Answer 1

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To generate hexagonal prism, you can CirclePoints[r, \[Phi]}, 6] together with ConvexHullMesh[]. This prism is defined by the radius $r$, height $h$, and it is rotated around the $z$-axis by the angle $\phi$.

a = 1;
c = 3;
p = ContourPlot3D[
   e2[kx, ky, kz] == 
    0, {kx, (-4 \[Pi])/(3 Sqrt[3] a), (4 \[Pi])/(3 Sqrt[
        3] a)}, {ky, (-2 \[Pi])/(3 a), (2 \[Pi])/(3 a)}, {kz, -\[Pi]/
     c, \[Pi]/c}, AxesLabel -> Automatic];

r = (4 \[Pi])/(3 Sqrt[3] a);
h = \[Pi]/c;
\[Phi] = 0;
hexagon = CirclePoints[{r, \[Phi]}, 6];
prism = ConvexHullMesh[(Append[#, -h/2] & /@ hexagon)~Join~(Append[#, h/2] & /@ hexagon)];
Show[p, Graphics3D[{EdgeForm[Black], FaceForm[None], prism}]]

You should appropriately change the parameters for the prism so that its dimensions match the Brillouin zone (I have forgotten my solid state physics, so I am not sure how exactly should the Fermi surface be positioned relative to the hexagonal lattice).

Mathematica graphics

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