Terahertz and Infrared Plasmon Polaritons in PtTe₂ Type-II Dirac Topological Semimetal

Surface plasmon polaritons (SPPs) are electromagnetic excitations existing at the interface between a metal and a dielectric. SPPs provide a promising path in nanophotonic devices for light manipulation at the micro and nanoscale with applications in optoelectronics, biomedicine, and energy harvesting. Recently, SPPs are extended to unconventional materials like graphene, transparent oxides, superconductors, and topological systems characterized by linearly dispersive electronic bands. In this respect, 3D Dirac and Weyl semimetals offer a promising frontier for infrared (IR) and terahertz (THz) radiation tuning by topologically-protected SPPs. In this work, the THz-IR optical response of platinum ditelluride (PtTe₂) type-II Dirac topological semimetal films grown on Si substrates is investigated. SPPs generated on microscale ribbon arrays of PtTe₂ are detected in the far-field limit, finding an excellent agreement among measurements, theoretical models, and electromagnetic simulation data. The far-field measurements are further supported by near-field IR data which indicate a strong electric field enhancement due to the SPP excitation near the ribbon edges. The present findings indicate that the PtTe₂ ribbon array appears an ideal active layout for geometrically tunable SPPs thus inspiring a new fashion of optically tunable materials in the technologically demanding THz and IR spectrum.