  Coulomb interactions play an essential role in atomically-thin materials. On
one hand, they are strong and long-ranged in layered systems due to the lack of
environmental screening. On the other hand, they can be efficiently tuned by
means of surrounding dielectric materials. Thus all physical properties which
decisively depend on the exact structure of the electronic interactions can be
in principle efficiently controlled and manipulated from the outside via
Coulomb engineering. Here, we show how this concept can be used to create
fundamentally new plasmonic waveguides in metallic layered materials. We
discuss in detail how dielectrically structured environments can be utilized to
non-invasively confine plasmonic excitations in an otherwise homogeneous
metallic 2D system by modification of its many-body interactions. We define
optimal energy ranges for this mechanism and demonstrate plasmonic confinement
within several nanometers. In contrast to conventional functionalization
mechanisms, this scheme relies on a purely many-body concept and does not
involve any direct modifications to the active material itself.
