Accidental degeneracy of double Dirac cones in a phononic crystal

Abstract
Artificial honeycomb lattices with Dirac cone dispersion provide a macroscopic platform to study the massless Dirac quasiparticles and their novel geometric phases. In this paper, a quadruple-degenerate state is achieved at the center of the Brillouin zone in a two-dimensional honeycomb lattice phononic crystal, which is a result of accidental degeneracy of two double-degenerate states. In the vicinity of the quadruple-degenerate state, the dispersion relation is linear. Such quadruple degeneracy is analyzed by rigorous representation theory of groups. Using method, a reduced Hamiltonian is obtained to describe the linear Dirac dispersion relations of this quadruple-degenerate state, which is well consistent with the simulation results. Near such accidental degeneracy, we observe some unique properties in wave propagating, such as defect-insensitive propagating character and the Talbot effect.

Citation
Chen Z-G, Ni X, Wu Y, He C, Sun X-C, et al. (2014) Accidental degeneracy of double Dirac cones in a phononic crystal. Sci Rep 4. doi:10.1038/srep04613.

Publisher
Springer Nature

Journal
Scientific Reports

DOI
10.1038/srep04613

PubMed ID
24714512

PubMed Central ID
PMC4070013

arXiv
1402.2154

Additional Links
http://arxiv.org/abs/1402.2154

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