Tunable Plasmons in Large-Area WTe2 Thin Films

The observation of electrically tunable and highly confined plasmons in graphene has stimulated the exploration of interesting properties of plasmons in other two-dimensional materials. Recently, hyperbolic plasmon resonance modes have been observed in exfoliated WTe2 films, a type-II Weyl semimetal with layered structure, providing a platform for the assembly of plasmons with hyperbolicity and exotic topological properties. However, the plasmon modes were observed in relatively thick and small-area films, which restrict the tunability and application for plasmons. Here, large-area (approximately cm) WTe2 films with different thicknesses are grown by the chemical vapor deposition method, in which plasmon resonance modes are observed in films with different thicknesses down to about 8 nm. Hybridization of plasmon and surface polar phonons of the substrate is revealed by mapping the plasmon dispersion. The plasmon frequency is demonstrated to be tunable by changing the temperature and film thickness. Our results facilitate the development of a tunable and scalable WTe2 plasmonic system for revealing topological properties and towards various applications in sensing, imaging, and light modulation.