Plasmonic Enhancement of Second Harmonic Generation in Weyl Semimetal TaAs

Abstract In this work a hybrid nanoplasmonic‐Weyl Semimetal (WSM) structure is realized for the first time utilizing silver nanopatch antennas and WSM Tantalum Arsenide (TaAs). The studied hybrid WSM‐nanoplasmonic structure demonstrated a substantial, over x4.5 enhancement of the second harmonic generation (SHG) process compared to a bare TaAs film. To realize the hybrid structure while preserving TaAs properties, a scalable, non‐destructive manufacturing approach is developed that involves the fabrication of TaAs flakes from single crystalline TaAs, overgrowth of a silicon nitride overlayer, and drop‐casting of silver nanopatch antennas. The strong polarization response of both the bare flakes, along with the hybrid‐nanoplasmonic cavities demonstrates that this approach uniquely preserves the TaAs crystal structure and its optical response while providing significant enhancement of the nonlinear properties. The developed method allows leveraging the capabilities of plasmonics to control and enhance light‐matter interactions at the nanometer scale to access and engineer WSM response. This work is the first step towards high‐performance nanophotonic devices utilizing WSM topological properties.