a, 3D band structure of the PhC in Fig. 1 on the high symmetry plane k_y=0 illustrating that the 1st mirror-even band (magenta cone) intersects with a pair of mirror -odd bands (light blue surfaces) along two red nodal rings, and the two odd bands coincide along the blue Kramers-like NL. The pair of orange dots shows the nexus points of the 3 NLs. b, c, and d, Zoomed-in band structures around the NP in three sections, respectively. e, Iso-frequency surfaces around the NP where the black tangential lines are obtained from the 1st-order k?p Hamiltonian. f, Band structure of a PhC with broken hidden symmetry.
by Zhongfei Xiong, Ruo-Yang Zhang2, Rui Yu, C. T. Chan, Yuntian Chen