Broadband and ultra-thin terahertz metamaterial absorber based on multi-circular patches G. D. Wang, M. H. Liu, X. W. Hu, L. H. Kong, L. L. Cheng and Z. Q. Chen Eur. Phys. J. B, 86 7 (2013) 304 Published online: 03 July 2013 DOI: 10.1140/epjb/e2013-30879-7