Non-Hermitian Thermophotonic Funneling via Nonreciprocal Surface Waves

Non-Hermitian photonics revolutionizes the understanding and manipulation of wave propagation in open systems. However, due to the interplay of non-Hermitian light-matter interactions and complex long-range couplings, miniaturizing topological features into deep-subwavelength regimes remains a significant challenge, and state-of-the-art explorations have thus far remained on the reciprocal topological photonic states. Here, we introduce nonreciprocal surface waves into deep-subwavelength dimerized lattices to theoretically demonstrate an efficient thermophotonic funnel. The system comprises an array of silicon carbide nanoparticles coupled with a graphene substrate. Under electrical bias, the graphene substrate enables the breaking of time-reversal symmetry in a magnetic-free and compact configuration, while also providing additional channels for photonic-based heat flow. The synergy between nonreciprocal surface waves and collective thermophotonic interactions drives all eigenstates to collapse toward the truncation of the lattice, exhibiting up to a 278-fold enhancement in one-way radiative field intensity. The topological fingerprints of this funneling effect are characterized by point-gap topology and complex-eigenspectrum braiding. Our findings bridge non-Hermitian physics and nonreciprocal thermophotonics, unlocking new possibilities for topological applications.