Nano-wrinkle waveguides for programmable polariton channeling

Abstract

Abstract The intrinsic planarity of two-dimensional (2D) van der Waals (vdW) polaritonic media inherently limits the lateral confinement of vdW polaritons. Here, we transcend this geometric limit by introducing a deterministic strategy to engineer non-planar nano-wrinkle waveguides in hexagonal boron nitride (hBN) via controlled thermal buckling. By exploiting the thermal expansion features of a calcite substrate, we generate uniaxial stress during cooling, which naturally forms high-curvature wrinkles in the overlying hBN superstrate. These wrinkles function as reconfigurable channel waveguides, guiding polaritons along predefined paths, and nano-hole patterning of such heterostructures offers programmable routing. Cryogenic near-field imaging and simulations reveal a wrinkle-guided polariton mode with a wavevector and dispersion governed by the wrinkle geometry and distinct from substrate-supported branches. Their hybridization allows precise tuning of modal confinement via hBN thickness variation. Concurrently, these structures guide polariton-mediated heat flow, establishing a medium-free mechanism for nanoscale thermal management. More broadly, our approach establishes a universal route for the geometric control of light and heat in two-dimensional materials.