TY - JOUR AB - Phonon polaritons—light coupled to lattice vibrations—in polar van der Waals crystals are promising candidates for controlling the flow of energy on the nanoscale due to their strong field confinement, anisotropic propagation and ultra-long lifetime in the picosecond range1,2,3,4,5. However, the lack of tunability of their narrow and material-specific spectral range—the Reststrahlen band—severely limits their technological implementation. Here, we demonstrate that intercalation of Na atoms in the van der Waals semiconductor α-V2O5 enables a broad spectral shift of Reststrahlen bands, and that the phonon polaritons excited show ultra-low losses (lifetime of 4 ± 1 ps), similar to phonon polaritons in a non-intercalated crystal (lifetime of 6 ± 1 ps). We expect our intercalation method to be applicable to other van der Waals crystals, opening the door for the use of phonon polaritons in broad spectral bands in the mid-infrared domain. AU - Taboada-Gutiérrez, Javier AU - Álvarez-Pérez, Gonzalo AU - Duan, Jiahua AU - Ma, Weiliang AU - Crowley, Kyle AU - Prieto Gonzalez, Ivan AU - Bylinkin, Andrei AU - Autore, Marta AU - Volkova, Halyna AU - Kimura, Kenta AU - Kimura, Tsuyoshi AU - Berger, M. H. AU - Li, Shaojuan AU - Bao, Qiaoliang AU - Gao, Xuan P.A. AU - Errea, Ion AU - Nikitin, Alexey Y. AU - Hillenbrand, Rainer AU - Martín-Sánchez, Javier AU - Alonso-González, Pablo ID - 7792 JF - Nature Materials SN - 14761122 TI - Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation VL - 19 ER -