Fig. 1: The 3D PTI without spin–orbit coupling.
From: Three-dimensional photonic topological insulator without spin–orbit coupling
a Unit cell of the 3D PTI. The geometrical parameters are given as a = 11 mm, az = 9.7 mm, L = 4.4 mm, Lz = 3.7 mm, w = 1 mm, and D = 1.8 mm. The golden region is copper. b The 3D BZ and its projection to the kx- and kz-axes. Inset: a quadratic band crossing at a C4-invariant momentum \(\bar{M}\) in the (001) surface BZ. c Simulated bulk bandstructure. d Electric field distribution (colormap) and polarization density (arrows) of bulk eigenmodes at \(\bar{M}\) for the (i) first, (ii) second, and (iii) third bands. + and − indicate where electric fields are divergent and convergent, respectively.
