Complete 72-parametric classification of surface plasmon polaritons in quartic metamaterials

We propose a general and complete classification of all possible new and old kinds of surface plasmon polaritons (SPPs) that can propagate at boundaries of arbitrary linear, local bi-anisotropic media, including the quartic metamaterials. In particular, we introduce a new kind of generic bi-exponential SPPs with arbitrary frequency, wavelength, propagation direction, and penetration depths and fields. We show that any such an SPP is supported by a broad 72-parametric invariance class of pairs of interfacing media. A member of each invariance class is a pair of anisotropic materials without magnetoelectric couplings.