Photonic and phononic crystals are structured materials with periodic modulations in their physical parameters. Due to their wide applications in molding the flow of electromagnetic, acoustic and elastic waves, they have attracted much attention especially in the band gaps. 
Recently, an interesting type of band structure was found for phoXonic crystals, which is a classical analogue of the Dirac cones.  We used the k.p method to study such type of band structures and

  • offered a “selection rule” to examine the linearity of the dispersion based on the group analysis  
  • predicted the slope of the linear dispersion
  • clarified the concepts of the Dirac cone and the Dirac-like cone by calculating the Berry phase 

​Prof. Zhaoqing Zhang, Prof. C. T. Chan, Prof. Jun Mei, Ms. Yan Li

​Jun Mei, Ying Wu, C. T. Chan, and Zhao-Qing Zhang, “First-principles study of Dirac andDirac-like cones in phononic and photonic crystals” Phys. Rev. B 86, 035141 (2012).