Surface plasmon polaritons excitation at the interface of graphene and sodium mediaJehan Akbar, Xu Bin, Lianping Hou, John H. Marsh and Xuefeng LiuEur. Phys. J. Plus, 137 3 (2022) 291DOI: https://doi.org/10.1140/epjp/s13360-021-02275-1