Surface plasmon polaritons excitation at the interface of graphene and sodium media Jehan Akbar, Xu Bin, Lianping Hou, John H. Marsh and Xuefeng Liu Eur. Phys. J. Plus, 137 3 (2022) 291 Published online: 01 March 2022 DOI: 10.1140/epjp/s13360-021-02275-1