  In this paper a thorough theoretical study of a new class of collective
excitations, dubbed hyperbolic surface phonon plasmon polaritons, is performed.
This new type of light-matter excitations are shown to have unique properties
that allows to explore them both as the basis of ultra-sensitive devices to the
dielectric nature of its surroundings. The system is a van der Waals
heterostructure -- a layered metamaterial, composed of different 2D materials
in direct contact one with another, namely graphene ribbons and hexagonal boron
nitride slabs of nanometric size. In the paper we discuss the spectrum of these
new class of excitations, the associated electromagnetic fields, the
sensitivity to the dielectric function of its surroundings, and the absorption
spectrum. All this is accomplished using an analytical model that considerably
diminishes the computational burden, as well as elucidates the underling
physical mechanism of the excitations supported by the device.
