A wide-angle broadband absorber in graphene-based hyperbolic metamaterialsRenxia Ning, Shaobin Liu, Haifeng Zhang, Borui Bian and Xiangkun KongEur. Phys. J. Appl. Phys., 68 2 (2014) 20401DOI: https://doi.org/10.1051/epjap/2014140221