Dear MPB User Community,
I am attempting to produce the band diagram for the single network gyroid shown
in Figure 2a of "Weyl points and line nodes in gyroid photonic crystals", by
Ling Lu*, Liang Fu, John D. Joannopoulos and Marin Soljacˇic´, Nature Photonics
2013.42. Although MPB (via my ctl file) accurately produces the band gap and
many features of the archived diagram, the first and second bands strangely go
almost to zero at k-points H': 2pi (0,0,1)/a and H: 2pi(0,1,0). Also, a plot of
the epsilon field looks good.
This feature does not appear in Lu's plot. I do not understand what has gone
wrong. If someone could help me fix the problem with my simulation, I would be
very grateful. My ctl file is shown below.
Thank you.
Doug Nance
; BCC lattice for gyroid
; t = 0 <=> phi = 0.5
; t = -1 <=> phi = 0.17
; t = -0.3 <=> phi = 0.40
;
(define pi 3.141592654)
(define a 1.0)
(define num 2.0)
(define numpioa (/ (* num pi) a))
(define fr 0.0)
(define t 1.1)
(define epsc 16.0)
(define epsa 1.0)
(define sx 0.0)
(define cx 0.0)
(define sy 0.0)
(define cy 0.0)
(define sz 0.0)
(define cz 0.0)
(define (px p) (vector3-x (lattice->cartesian p)))
(define (py p) (vector3-y (lattice->cartesian p)))
(define (pz p) (vector3-z (lattice->cartesian p)))
(define (eps-func p)
(set! sx (sin (* numpioa (px p))))
(set! cx (cos (* numpioa (px p))))
(set! sy (sin (* numpioa (py p))))
(set! cy (cos (* numpioa (py p))))
(set! sz (sin (* numpioa (pz p))))
(set! cz (cos (* numpioa (pz p))))
(set! fr (+ (* sx cy) (+ (* sy cz) (* cx sz))))
(make dielectric (epsilon
(if (> fr t) epsc epsa ))))
(set! geometry-lattice (make lattice
(basis-size (sqrt 0.75) (sqrt 0.75) (sqrt 0.75))
(basis1 -1 1 1)
(basis2 1 -1 1)
(basis3 1 1 -1)))
(set! k-points (interpolate 4 (list
(vector3 0 0 1) ; H'
(vector3 0 0 0) ; Gamma
(vector3 -0.5 0.5 0.5) ; P
(vector3 0 0 1) ; H'
(vector3 0 0.5 0.5) ; N
(vector3 0 0 0) ; Gamma
(vector3 0 1 0) ; H
(vector3 -0.5 0.5 0.5) ; P
(vector3 0 0.5 0.5)))) ; N
(set! default-material (make material-function
(material-func eps-func)))
(set-param! resolution 32)
(set-param! mesh-size 3)
(set-param! num-bands 6)
(run)
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