Polarization-independent omnidirectional band gaps in heterostructures containing negative-index materialsX. H. Deng, T. B. Wang, J. T. Liu, J. H. Huang, T. B. Yu, Q. H. Liao and N. H. LiuEur. Phys. J. B, 78 1 (2010) 7-12DOI: https://doi.org/10.1140/epjb/e2010-00298-7