Observation of tunable plasmons in large area type-II Weyl semimetal films

The observation of the highly tunable and confined plasmons in Graphene has stimulated the exploration of plasmons in other 2D materials. Here, for the first time, plasmonic resonance modes are observed in CVD-grown large area films of WTe₂, which is known as a type-II Weyl semimetal, by far-infrared absorption spectroscopy. Plasmon-phonon hybridization is revealed by mapping the plasmon dispersion on Si/SiO2 substrates. The plasmon frequency is tunable by changing the temperature and film thickness. Moreover, the plasmon modes are still observable with film thickness down to 8 nm, indicating the potential for tuning by gate. Our results represent a first look at the plasmon in large area CVD-grown Weyl semimetal films and suggest a practical platform to experimentally study the topological plasmons.