  The large oscillator strength of excitons in transition metal dichalcogenide
layers facilitates the formation of exciton-polariton resonances for monolayers
and van-der-Waals heterostructures embedded in optical microcavities. Here, we
show, that locally changing the number of layers in a WSe2/hBN/WSe2
van-der-Waals heterostructure embedded in a monolithic, high-quality-factor
cavity gives rise to a local variation of the coupling strength. This effect
yields a polaritonic stair case potential, which we demonstrate at room
temperature. Our result paves the way towards engineering local polaritonic
potentials at length scales down to atomically sharp interfaces, based on
purely modifying its real part contribution via the coherent light-matter
coupling strength g.
